Sonar (originally an acronym for SOund Navigation And Ranging) is a technique that uses sound propagation (usually underwater, as in Submarine navigation) to navigate, communicate with or detect other vessels. Two types of technology share the name "sonar": ''passive'' sonar is essentially listening for the sound made by vessels; ''active'' sonar is emitting pulses of sounds and listening for echoes. Sonar may be used as a means of acoustic location and of measurement of the echo characteristics of "targets" in the water. Acoustic location in air was used before the introduction of radar. Sonar may also be used in air for robot navigation, and SODAR (an upward looking in-air sonar) is used for atmospheric investigations. The term ''sonar'' is also used for the equipment used to generate and receive the sound. The acoustic frequencies used in sonar systems vary from very low (infrasonic) to extremely high (ultrasonic). The study of underwater sound is known as underwater acoustics or hydroacoustics.

History

Although some animals (dolphins and bats) have used sound for communication and object detection for millions of years, use by humans in the water is initially recorded by Leonardo Da Vinci in 1490: a tube inserted into the water was said to be used to detect vessels by placing an ear to the tube.

In the 19th century an underwater bell was used as an ancillary to lighthouses to provide warning of hazards.

The use of sound to 'echo locate' underwater in the same way as bats use sound for aerial navigation seems to have been prompted by the ''Titanic'' disaster of 1912. The world's first patent for an underwater echo ranging device was filed at the British Patent Office by English meteorologist Lewis Richardson a month after the sinking of the Titanic, and a German physicist Alexander Behm obtained a patent for an echo sounder in 1913.

The Canadian engineer Reginald Fessenden, while working for the Submarine Signal Company in Boston, built an experimental system beginning in 1912, a system later tested in Boston Harbor, and finally in 1914 from the U.S. Revenue (now Coast Guard) Cutter Miami on the Grand Banks off Newfoundland Canada. In that test, Fessenden demonstrated depth sounding, underwater communications (Morse Code) and echo ranging (detecting an iceberg at two miles (3 km) range). The so-called Fessenden oscillator, at ca. 500 Hz frequency, was unable to determine the bearing of the berg due to the 3 metre wavelength and the small dimension of the transducer's radiating face (less than 1 metre in diameter). The ten Montreal-built British H class submarines launched in 1915 were equipped with a Fessenden oscillator.

During World War I the need to detect submarines prompted more research into the use of sound. The British made early use of underwater hydrophones, while the French physicist Paul Langevin, working with a Russian immigrant electrical engineer, Constantin Chilowski, worked on the development of active sound devices for detecting submarines in 1915 using quartz. Although piezoelectric and magnetostrictive transducers later superseded the electrostatic transducers they used, this work influenced future designs. Lightweight sound-sensitive plastic film and fibre optics have been used for hydrophones (acousto-electric transducers for in-water use), while Terfenol-D and PMN (lead magnesium niobate) have been developed for projectors.

ASDIC

In 1916, under the British Board of Invention and Research, Canadian physicist Robert William Boyle took on the active sound detection project with A B Wood, producing a prototype for testing in mid 1917. This work, for the Anti-Submarine Division of the British Naval Staff, was undertaken in utmost secrecy, and used quartz piezoelectric crystals to produce the world's first practical underwater active sound detection apparatus. To maintain secrecy no mention of sound experimentation or quartz was made - the word used to describe the early work ('supersonics') was changed to 'ASD'ics, and the quartz material to 'ASD'ivite: hence the British acronym ''ASDIC''. In 1939, in response to a question from the Oxford English Dictionary, the Admiralty made up the story that it stood for 'Allied Submarine Detection Investigation Committee', and this is still widely believed, though no committee bearing this name has been found in the Admiralty archives.

By 1918, both France and Britain had built prototype active systems. The British tested their ASDIC on HMS ''Antrim'' in 1920, and started production in 1922. The 6th Destroyer Flotilla had ASDIC-equipped vessels in 1923. An anti-submarine school, HMS ''Osprey'', and a training flotilla of four vessels were established on Portland in 1924. The US Sonar QB set arrived in 1931.

By the outbreak of World War II, the Royal Navy had five sets for different surface ship classes, and others for submarines, incorporated into a complete anti-submarine attack system. The effectiveness of early ASDIC was hamstrung by the use of the depth charge as an anti-submarine weapon. This required an attacking vessel to pass over a submerged contact before dropping charges over the stern, resulting in a loss of ASDIC contact in the moments leading up to attack. The hunter was effectively firing blind, during which time a submarine commander could take evasive action. This situation was remedied by using several ships cooperating and by the adoption of "ahead throwing weapons", such as Hedgehog and later Squid, which projected warheads at a target ahead of the attacker and thus still in ASDIC contact. Developments during the war resulted in British ASDIC sets which used several different shapes of beam, continuously covering blind spots. Later, acoustic torpedoes were used.

At the start of World War II, British ASDIC technology was transferred for free to the United States. Research on ASDIC and underwater sound was expanded in the UK and in the US. Many new types of military sound detection were developed. These included sonobuoys, first developed by the British in 1944 under the codename ''High Tea'', dipping/dunking sonar and mine detection sonar. This work formed the basis for post war developments related to countering the nuclear submarine. Work on sonar had also been carried out in the Axis countries, notably in Germany, which included countermeasures. At the end of World War II this German work was assimilated by Britain and the US. Sonars have continued to be developed by many countries, including Russia, for both military and civil uses. In recent years the major military development has been the increasing interest in low frequency active systems.

SONAR

During the 1930s American engineers developed their own underwater sound detection technology and important discoveries were made, such as thermoclines, that would help future development. After technical information was exchanged between the two countries during the Second World War, Americans began to use the term ''SONAR'' for their systems, coined as the equivalent of RADAR.

Performance factors

The detection, classification and localisation performance of a sonar depends on the environment and the receiving equipment, as well as the transmitting equipment in an active sonar or the target radiated noise in a passive sonar.

Sound propagation

Sonar operation is affected by variations in sound speed, particularly in the vertical plane. Sound travels more slowly in fresh water than in sea water, though the difference is small. The speed is determined by the water's bulk modulus and mass density. The bulk modulus is affected by temperature, dissolved impurities (usually salinity), and pressure. The density effect is small. The speed of sound (in feet per second) is approximately:

:4388 + (11.25 × temperature (in °F)) + (0.0182 × depth (in feet)) + salinity (in parts-per-thousand ).

This empirically derived approximation equation is reasonably accurate for normal temperatures, concentrations of salinity and the range of most ocean depths. Ocean temperature varies with depth, but at between 30 and 100 meters there is often a marked change, called the thermocline, dividing the warmer surface water from the cold, still waters that make up the rest of the ocean. This can frustrate sonar, because a sound originating on one side of the thermocline tends to be bent, or refracted, through the thermocline. The thermocline may be present in shallower coastal waters. However, wave action will often mix the water column and eliminate the thermocline. Water pressure also affects sound propagation: higher pressure increases the sound speed, which causes the sound waves to refract away from the area of higher sound speed. The mathematical model of refraction is called Snell's law.

If the sound source is deep and the conditions are right, propagation may occur in the 'deep sound channel'. This provides extremely low propagation loss to a receiver in the channel. This is because of sound trapping in the channel with no losses at the boundaries. Similar propagation can occur in the 'surface duct' under suitable conditions. However in this case there are reflection losses at the surface.

In shallow water propagation is generally by repeated reflection at the surface and bottom, where considerable losses can occur.

Sound propagation is affected by absorption in the water itself as well as at the surface and bottom. This absorption depends upon frequency, with several different mechanisms in sea water. Long-range sonar uses low frequencies to minimise absorption effects.

The sea contains many sources of noise that interfere with the desired target echo or signature. The main noise sources are waves and shipping. The motion of the receiver through the water can also cause speed-dependent low frequency noise.

Scattering

When active sonar is used, scattering occurs from small objects in the sea as well as from the bottom and surface. This can be a major source of interference. This acoustic scattering is analogous to the scattering of the light from a car's headlights in fog: a high-intensity pencil beam will penetrate the fog to some extent, but broader-beam headlights emit much light in unwanted directions, much of which is scattered back to the observer, overwhelming that reflected from the target ("white-out"). For analogous reasons active sonar needs to transmit in a narrow beam to minimise scattering.

Target characteristics

The sound ''reflection'' characteristics of the target of an active sonar, such as a submarine, are known as its target strength. A complication is that echoes are also obtained from other objects in the sea such as whales, wakes, schools of fish and rocks.

Passive sonar detects the target's ''radiated'' noise characteristics. The radiated spectrum comprises a continuous spectrum of noise with peaks at certain frequencies which can be used for classification.

Countermeasures

''Active'' (powered) countermeasures may be launched by a submarine under attack to raise the noise level, provide a large false target, and obscure the signature of the submarine itself.

''Passive'' (i.e., non-powered) countermeasures include:

Mounting noise-generating devices on isolating devices.

Sound-absorbent coatings on the hulls of submarines, for example anechoic tiles.

Active sonar

Active sonar uses a sound transmitter and a receiver. When the two are in the same place it is monostatic operation. When the transmitter and receiver are separated it is bistatic operation. When more transmitters (or more receivers) are used, again spatially separated, it is multistatic operation. Most sonars are used monostatically with the same array often being used for transmission and reception. Active sonobuoy fields may be operated multistatically.

Active sonar creates a pulse of sound, often called a "ping", and then listens for reflections (echo) of the pulse. This pulse of sound is generally created electronically using a sonar projector consisting of a signal generator, power amplifier and electro-acoustic transducer/array. A beamformer is usually employed to concentrate the acoustic power into a beam, which may be swept to cover the required search angles. Generally, the electro-acoustic transducers are of the Tonpilz type and their design may be optimised to achieve maximum efficiency over the widest bandwidth, in order to optimise performance of the overall system. Occasionally, the acoustic pulse may be created by other means, e.g. (1) chemically using explosives, or (2) airguns or (3) plasma sound sources.

To measure the distance to an object, the time from transmission of a pulse to reception is measured and converted into a range by knowing the speed of sound. To measure the bearing, several hydrophones are used, and the set measures the relative arrival time to each, or with an array of hydrophones, by measuring the relative amplitude in beams formed through a process called beamforming. Use of an array reduces the spatial response so that to provide wide cover multibeam systems are used. The target signal (if present) together with noise is then passed through various forms of signal processing, which for simple sonars may be just energy measurement. It is then presented to some form of decision device that calls the output either the required signal or noise. This decision device may be an operator with headphones or a display, or in more sophisticated sonars this function may be carried out by software. Further processes may be carried out to classify the target and localise it, as well as measuring its velocity.

The pulse may be at constant frequency or a chirp of changing frequency (to allow pulse compression on reception). Simple sonars generally use the former with a filter wide enough to cover possible Doppler changes due to target movement, while more complex ones generally include the latter technique. Since digital processing became available pulse compression has usually been implemented using digital correlation techniques. Military sonars often have multiple beams to provide all-round cover while simple ones only cover a narrow arc, although the beam may be rotated, relatively slowly, by mechanical scanning.

Particularly when single frequency transmissions are used, the Doppler effect can be used to measure the radial speed of a target. The difference in frequency between the transmitted and received signal is measured and converted into a velocity. Since Doppler shifts can be introduced by either receiver or target motion, allowance has to be made for the radial speed of the searching platform.

One useful small sonar is similar in appearance to a waterproof flashlight. The head is pointed into the water, a button is pressed, and the device displays the distance to the target. Another variant is a "fishfinder" that shows a small display with shoals of fish. Some civilian sonars (which are not designed for stealth) approach active military sonars in capability, with quite exotic three-dimensional displays of the area near the boat.

When active sonar is used to measure the distance from the transducer to the bottom, it is known as echo sounding. Similar methods may be used looking upward for wave measurement.

Active sonar is also used to measure distance through water between two sonar transducers or a combination of a hydrophone (underwater acoustic microphone) and projector (underwater acoustic speaker). A transducer is a device that can transmit and receive acoustic signals ("pings"). When a hydrophone/transducer receives a specific interrogation signal it responds by transmitting a specific reply signal. To measure distance, one transducer/projector transmits an interrogation signal and measures the time between this transmission and the receipt of the other transducer/hydrophone reply. The time difference, scaled by the speed of sound through water and divided by two, is the distance between the two platforms. This technique, when used with multiple transducers/hydrophones/projectors, can calculate the relative positions of static and moving objects in water.

In combat situations, an active pulse can be detected by an opponent and will reveal a submarine's position.

A very directional, but low-efficiency, type of sonar (used by fisheries, military, and for port security) makes use of a complex nonlinear feature of water known as non-linear sonar, the virtual transducer being known as a ''parametric array''.

Project ARTEMIS

Project ARTEMIS was a one-of-a-kind low-frequency sonar for surveillance that was deployed off Bermuda for several years in the early 1960s. The active portion was deployed from a World War II tanker, and the receiving array was a built into a fixed position on an offshore bank.

Transponder

This is an active sonar device that receives a stimulus and immediately (or with a delay) retransmits the received signal or a predetermined one.

Performance prediction

A sonar target is small relative to the sphere, centred around the emitter, on which it is located. Therefore, the power of the reflected signal is very low, several orders of magnitude less than the original signal. Even if the reflected signal was of the same power, the following example (using hypothetical values) shows the problem: Suppose a sonar system is capable of emitting a 10,000 W/m² signal at 1 m, and detecting a 0.001 W/m² signal. At 100 m the signal will be 1 W/m² (due to the inverse-square law). If the entire signal is reflected from a 10 m² target, it will be at 0.001 W/m² when it reaches the emitter, i.e. just detectable. However, the original signal will remain above 0.001 W/m² until 300 m. Any 10 m² target between 100 and 300 m using a similar or better system would be able to detect the pulse but would not be detected by the emitter. The detectors must be very sensitive to pick up the echoes. Since the original signal is much more powerful, it can be detected many times further than twice the range of the sonar (as in the example).

In active sonar there are two performance limitations, due to noise and reverberation. In general one or other of these will dominate so that the two effects can be initially considered separately.

In noise limited conditions at initial detection: ::::SL − 2TL + TS − (NL − DI) = DT where SL is the source level, TL is the transmission loss (or propagation loss), TS is the target strength, NL is the noise level, DI is the directivity index of the array (an approximation to the array gain) and DT is the detection threshold.

In reverberation limited conditions at initial detection (neglecting array gain): ::::SL − 2TL + TS = RL + DT where RL is the reverberation level and the other factors are as before.

Marine mammals

Active sonar may harm marine animals, although the precise mechanisms for this are not well understood. Some marine animals, such as whales and dolphins, use echolocation systems, sometimes called ''biosonar'' to locate predators and prey. It is conjectured that active sonar transmitters could confuse these animals and interfere with basic biological functions such as feeding and mating.

Hand-held sonar for use by a diver

The LIMIS (= Limpet Mine Imaging Sonar) is a hand-held or ROV-mounted imaging sonar for use by a diver. Its name is because it was designed for patrol divers (combat frogmen or Clearance Divers) to look for limpet mines in low visibility water. Links:

Abstract of article by the International Society for Optical Engineering

* Used to find debris from the Space Shuttle Columbia crash

* Used in fish passage research at hydropower facilities

The LUIS (= Lensing Underwater Imaging System) is another imaging sonar for use by a diver. Links:

* Used for counting salmon in a river

There is or was a small flashlight-shaped handheld sonar for divers, that merely displays range.

For the INSS = Integrated Navigation Sonar System see:

* an image.

* short description

* description

Passive sonar

Passive sonar listens without transmitting. It is often employed in military settings, although it is also used in science applications, ''e.g.'', detecting fish for presence/absence studies in various aquatic environments - see also passive acoustics and passive radar. In the very broadest usage, this term can encompass virtually any analytical technique involving remotely generated sound, though it is usually restricted to techniques applied in an aquatic environment.

Identifying sound sources

Passive sonar has a wide variety of techniques for identifying the source of a detected sound. For example, U.S. vessels usually operate 60 Hz alternating current power systems. If transformers or generators are mounted without proper vibration insulation from the hull or become flooded, the 60 Hz sound from the windings can be emitted from the submarine or ship. This can help to identify its nationality, as most European submarines have 50 Hz power systems. Intermittent sound sources (such as a wrench being dropped) may also be detectable to passive sonar. Until fairly recently, an experienced trained operator identified signals, but now computers may do this.

Passive sonar systems may have large sonic databases, but the sonar operator usually finally classifies the signals manually. A computer system frequently uses these databases to identify classes of ships, actions (i.e. the speed of a ship, or the type of weapon released), and even particular ships. Publications for classification of sounds are provided by and continually updated by the US Office of Naval Intelligence.

Noise limitations

Passive sonar on vehicles is usually severely limited because of noise generated by the vehicle. For this reason, many submarines operate nuclear reactors that can be cooled without pumps, using silent convection, or fuel cells or batteries, which can also run silently. Vehicles' propellers are also designed and precisely machined to emit minimal noise. High-speed propellers often create tiny bubbles in the water, and this cavitation has a distinct sound.

The sonar hydrophones may be towed behind the ship or submarine in order to reduce the effect of noise generated by the watercraft itself. Towed units also combat the thermocline, as the unit may be towed above or below the thermocline.

The display of most passive sonars used to be a two-dimensional waterfall display. The horizontal direction of the display is bearing. The vertical is frequency, or sometimes time. Another display technique is to color-code frequency-time information for bearing. More recent displays are generated by the computers, and mimic radar-type plan position indicator displays.

Performance prediction

Unlike active sonar, only one way propagation is involved. Because of the different signal processing used, the minimum detectable signal to noise ratio will be different. The equation for determining the performance of a passive sonar is: :::SL − TL = NL − DI + DT where SL is the source level, TL is the transmission loss, NL is the noise level, DI is the directivity index of the array (an approximation to the array gain) and DT is the detection threshold. The figure of merit of a passive sonar is: :::FOM = SL + DI − (NL + DT).

Warfare

Modern naval warfare makes extensive use of both passive and active sonar from water-borne vessels, aircraft and fixed installations. The relative usefulness of active versus passive sonar depends on the radiated noise characteristics of the target, generally a submarine. Although in World War II active sonar was used by surface craft—submarines avoided emitting pings which revealed their presence and position—with the advent of modern signal-processing passive sonar became preferred for initial detection. Submarines were then designed for quieter operation, and active sonar is now more used. In 1987 a division of Japanese company Toshiba reportedly sold machinery to the Soviet Union that allowed it to mill submarine propeller blades so that they became radically quieter, creating a huge security issue with their newer generation of submarines.

Active sonar gives the exact bearing to a target, and sometimes the range. Active sonar works the same way as radar: a signal is emitted. The sound wave then travels in many directions from the emitting object. When it hits an object, the sound wave is then reflected in many other directions. Some of the energy will travel back to the emitting source. The echo will enable the sonar system or technician to calculate, with many factors such as the frequency, the energy of the received signal, the depth, the water temperature, the position of the reflecting object, etc. Active sonar is used when the platform commander determines that it is more important to determine the position of a possible threat submarine than it is to conceal his own position. With surface ships it might be assumed that the threat is already tracking the ship with satellite data. Any vessel around the emitting sonar will detect the emission. Having heard the signal, it is easy to identify the sonar equipment used (usually with its frequency) and its position (with the sound wave's energy). Active sonar is similar to radar in that, while it allows detection of targets at a certain range, it also enables the emitter to be detected at a far greater range, which is undesirable.

Since active sonar reveals the presence and position of the operator, and does not allow exact classification of targets, it is used by fast (planes, helicopters) and by noisy platforms (most surface ships) but rarely by submarines. When active sonar is used by surface ships or submarines, it is typically activated very briefly at intermittent periods to minimise the risk of detection. Consequently active sonar is normally considered a backup to passive sonar. In aircraft, active sonar is used in the form of disposable sonobuoys that are dropped in the aircraft's patrol area or in the vicinity of possible enemy sonar contacts.

Passive sonar has several advantages. Most importantly, it is silent. If the target radiated noise level is high enough, it can have a greater range than active sonar, and allows the target to be identified. Since any motorized object makes some noise, it may in principle be detected, depending on the level of noise emitted and the ambient noise level in the area, as well as the technology used. To simplify, passive sonar "sees" around the ship using it. On a submarine, nose-mounted passive sonar detects in directions of about 270°, centered on the ship's alignment, the hull-mounted array of about 160° on each side, and the towed array of a full 360°. The invisible areas are due to the ship's own interference. Once a signal is detected in a certain direction (which means that something makes sound in that direction, this is called broadband detection) it is possible to zoom in and analyze the signal received (narrowband analysis). This is generally done using a Fourier transform to show the different frequencies making up the sound. Since every engine makes a specific sound, it is straightforward to identify the object. Databases of unique engine sounds are part of what is known as ''acoustic intelligence'' or ACINT.

Another use of passive sonar is to determine the target's trajectory. This process is called Target Motion Analysis (TMA), and the resultant "solution" is the target's range, course, and speed. TMA is done by marking from which direction the sound comes at different times, and comparing the motion with that of the operator's own ship. Changes in relative motion are analyzed using standard geometrical techniques along with some assumptions about limiting cases.

Passive sonar is stealthy and very useful. However, it requires high-tech electronic components and is costly. It is generally deployed on expensive ships in the form of arrays to enhance detection. Surface ships use it to good effect; it is even better used by submarines, and it is also used by airplanes and helicopters, mostly to a "surprise effect", since submarines can hide under thermal layers. If a submarine's commander believes he is alone, he may bring his boat closer to the surface and be easier to detect, or go deeper and faster, and thus make more sound.

Examples of sonar applications in military use are given below. Many of the civil uses given in the following section may also be applicable to naval use.

Anti-submarine warfare

Until recently, ship sonars were usually with hull mounted arrays, either amidships or at the bow. It was soon found after their initial use that a means of reducing flow noise was required. The first were made of canvas on a framework, then steel ones were used. Now domes are usually made of reinforced plastic or pressurised rubber. Such sonars are primarily active in operation. An example of a conventional hull mounted sonar is the SQS-56.

Because of the problems of ship noise, towed sonars are also used. These also have the advantage of being able to be placed deeper in the water. However, there are limitations on their use in shallow water. These are called towed arrays (linear) or variable depth sonars (VDS) with 2/3D arrays. A problem is that the winches required to deploy/recover these are large and expensive. VDS sets are primarily active in operation while towed arrays are passive.

An example of a modern active/passive ship towed sonar is Sonar 2087 made by Thales Underwater Systems.

Torpedoes

Modern torpedoes are generally fitted with an active/passive sonar. This may be used to home directly on the target, but wake following torpedoes are also used. An early example of an acoustic homer was the Mark 37 torpedo.

Torpedo countermeasures can be towed or free. An early example was the German Sieglinde device while the Bold was a chemical device. A widely used US device was the towed Nixie while MOSS submarine simulator was a free device. A modern alternative to the Nixie system is the UK Royal Navy S2170 Surface Ship Torpedo Defence system.

Mines

Mines may be fitted with a sonar to detect, localize and recognize the required target. Further information is given in acoustic mine and an example is the CAPTOR mine.

Mine countermeasures

Mine Countermeasure (MCM) Sonar, sometimes called "Mine and Obstacle Avoidance Sonar (MOAS)", is a specialised type of sonar used for detecting small objects. Most MCM sonars are hull mounted but a few types are VDS design. An example of a hull mounted MCM sonar is the Type 2193 while the SQQ-32 Mine-hunting sonar and Type 2093 systems are VDS designs. See also Minesweeper (ship)

Submarine navigation

Submarines rely on sonar to a greater extent than surface ships as they cannot use radar at depth. The sonar arrays may be hull mounted or towed. Information fitted on typical fits is given in Oyashio class submarine and Swiftsure class submarine.

Aircraft

Helicopters can be used for antisubmarine warfare by deploying fields of active/passive sonobuoys or can operate dipping sonar, such as the AQS-13. Fixed wing aircraft can also deploy sonobuoys and have greater endurance and capacity to deploy them. Processing from the sonobuoys or dipping sonar can be on the aircraft or on ship. Helicopters have also been used for mine countermeasure missions using towed sonars such as the AQS-20A

Underwater communications

Dedicated sonars can be fitted to ships and submarines for underwater communication. See also the section on the underwater acoustics page.

Ocean surveillance

For many years, the United States operated a large set of passive sonar arrays at various points in the world's oceans, collectively called Sound Surveillance System (SOSUS) and later Integrated Undersea Surveillance System (IUSS). A similar system is believed to have been operated by the Soviet Union. As permanently mounted arrays in the deep ocean were utilised, they were in very quiet conditions so long ranges could be achieved. Signal processing was carried out using powerful computers ashore. With the ending of the Cold War a SOSUS array has been turned over to scientific use.

In the United States Navy, a special badge known as the Integrated Undersea Surveillance System Badge is awarded to those who have been trained and qualified in its operation.

Underwater security

Sonar can be used to detect frogmen and other scuba divers. This can be applicable around ships or at entrances to ports. Active sonar can also be used as a deterrent and/or disablement mechanism. One such device is the Cerberus system.

See Underwater Port Security System and Anti-frogman techniques#Ultrasound detection.

Hand-held sonar

Limpet Mine Imaging Sonar (LIMIS) is a hand-held or ROV-mounted imaging sonar designed for patrol divers (combat frogmen or clearance divers) to look for limpet mines in low visibility water.

The LUIS is another imaging sonar for use by a diver.

Integrated Navigation Sonar System (INSS) is a small flashlight-shaped handheld sonar for divers that displays range.

Intercept sonar

This is a sonar designed to detect and locate the transmissions from hostile active sonars. An example of this is the Type 2082 fitted on the British Vanguard class submarines.

Civilian applications

Fisheries

Fishing is an important industry that is seeing growing demand, but world catch tonnage is falling as a result of serious resource problems. The industry faces a future of continuing worldwide consolidation until a point of sustainability can be reached. However, the consolidation of the fishing fleets are driving increased demands for sophisticated fish finding electronics such as sensors, sounders and sonars. Historically, fishermen have used many different techniques to find and harvest fish. However, acoustic technology has been one of the most important driving forces behind the development of the modern commercial fisheries.

Sound waves travel differently through fish than through water because a fish's air-filled swim bladder has a different density than seawater. This density difference allows the detection of schools of fish by using reflected sound. Acoustic technology is especially well suited for underwater applications since sound travels farther and faster underwater than in air. Today, commercial fishing vessels rely almost completely on acoustic sonar and sounders to detect fish. Fishermen also use active sonar and echo sounder technology to determine water depth, bottom contour, and bottom composition.

Companies such as Raymarine UK, Marport Canada, Wesmar, Furuno, Krupp, and Simrad make a variety of sonar and acoustic instruments for the deep sea commercial fishing industry. For example, net sensors take various underwater measurements and transmit the information back to a receiver onboard a vessel. Each sensor is equipped with one or more acoustic transducers depending on its specific function. Data is transmitted from the sensors using wireless acoustic telemetry and is received by a hull mounted hydrophone. The analog signals are decoded and converted by a digital acoustic receiver into data which is transmitted to a bridge computer for graphical display on a high resolution monitor.

Echo sounding

An echo-sounder sends an acoustic pulse directly downwards to the seabed and records the returned echo. The sound pulse is generated by a transducer that emits an acoustic pulse and then “listens” for the return signal. The time for the signal to return is recorded and converted to a depth measurement by calculating the speed of sound in water. As the speed of sound in water is around 1,500 metres per second, the time interval, measured in milliseconds, between the pulse being transmitted and the echo being received, allows bottom depth and targets to be measured.

The value of underwater acoustics to the fishing industry has led to the development of other acoustic instruments that operate in a similar fashion to echo-sounders but, because their function is slightly different from the initial model of the echo-sounder, have been given different terms.

Net location

The net sounder is an echo sounder with a transducer mounted on the headline of the net rather than on the bottom of the vessel. Nevertheless, to accommodate the distance from the transducer to the display unit, which is much greater than in a normal echo-sounder, several refinements have to be made. Two main types are available. The first is the cable type in which the signals are sent along a cable. In this case there has to be the provision of a cable drum on which to haul, shoot and stow the cable during the different phases of the operation. The second type is the cable less net-sounder – such as Marport’s Trawl Explorer - in which the signals are sent acoustically between the net and hull mounted receiver/hydrophone on the vessel. In this case no cable drum is required but sophisticated electronics are needed at the transducer and receiver.

The display on a net sounder shows the distance of the net from the bottom (or the surface), rather than the depth of water as with the echo-sounder's hull-mounted transducer. Fixed to the headline of the net, the footrope can usually be seen which gives an indication of the net performance. Any fish passing into the net can also be seen, allowing fine adjustments to be made to catch the most fish possible. In other fisheries, where the amount of fish in the net is important, catch sensor transducers are mounted at various positions on the cod-end of the net. As the cod-end fills up these catch sensor transducers are triggered one by one and this information is transmitted acoustically to display monitors on the bridge of the vessel. The skipper can then decide when to haul the net.

Modern versions of the net sounder, using multiple element transducers, function more like a sonar than an echo sounder and show slices of the area in front of the net and not merely the vertical view that the initial net sounders used.

The sonar is an echo-sounder with a directional capability that can show fish or other objects around the vessel.good

Ship velocity measurement

Sonars have been developed for measuring a ship's velocity either relative to the water or to the bottom.

ROV and UUV

Small sonars have been fitted to Remotely Operated Vehicles (ROV) and Unmanned Underwater Vehicles (UUV) to allow their operation in murky conditions. These sonars are used for looking ahead of the vehicle. The Long-Term Mine Reconnaissance System is an UUV for MCM purposes.

Vehicle location

Sonars which act as beacons are fitted to aircraft to allow their location in the event of a crash in the sea. Short and Long Baseline sonars may be used for caring out the location, such as LBL.

Scientific applications

Biomass estimation

Detection of fish, and other marine and aquatic life, and estimation their individual sizes or total biomass using active sonar techniques. As the sound pulse travels through water it encounters objects that are of different density or acoustic characteristics than the surrounding medium, such as fish, that reflect sound back toward the sound source. These echoes provide information on fish size, location, abundance and behavior. Data is usually processed and analysed using a variety of software such as Echoview. See Also: Hydroacoustics and Fisheries Acoustics.

Wave measurement

An upward looking echo sounder mounted on the bottom or on a platform may be used to make measurements of wave height and period. From this statistics of the surface conditions at a location can be derived.

Water velocity measurement

Special short range sonars have been developed to allow measurements of water velocity.

Bottom type assessment

Sonars have been developed that can be used to characterise the sea bottom into, for example, mud, sand, and gravel. Relatively simple sonars such as echo sounders can be promoted to seafloor classification systems via add-on modules, converting echo parameters into sediment type. Different algorithms exist, but they are all based on changes in the energy or shape of the reflected sounder pings. Advanced substrate classification analysis can be achieved using calibrated (scientific) echosounders and parametric or fuzzy-logic analysis of the acoustic data (See: Acoustic Seabed Classification)

Bottom topography measurement

Side-scan sonars can be used to derive maps of the topography of an area by moving the sonar across it just above the bottom. Low frequency sonars such as GLORIA have been used for continental shelf wide surveys while high frequency sonars are used for more detailed surveys of smaller areas.

Sub-bottom profiling

Powerful low frequency echo-sounders have been developed for providing profiles of the upper layers of the ocean bottom.

Synthetic aperture sonar

Various synthetic aperture sonars have been built in the laboratory and some have entered use in mine-hunting and search systems. An explanation of their operation is given in synthetic aperture sonar.

Parametric sonar

Parametric sources use the non-linearity of water to generate the difference frequency between two high frequencies. A virtual end-fire array is formed. Such a projector has advantages of broad bandwidth, narrow beamwidth, and when fully developed and carefully measured it has no obvious sidelobes: see Parametric array. Its major disadvantage is very low efficiency of only a few percent. P.J. Westervelt's seminal 1963 JASA paper summarizes the trends involved.

See also

Acoustic Doppler Current Profiler

Acoustic Tags

Animal echolocation

Baffles (submarine)

Beached whale

Beamforming

Bistatic sonar

Diver Detection Sonar

Echo Sounding

Fish finder

Hydroacoustics

Ocean acoustic tomography

Radar

Passive Radar

Lead zirconate titanate or PZT, a piezoelectric material used for ultrasonic transducers

Scientific Echosounder

Side-scan sonar

SOFAR channel

Sonar 2087

Sonobuoy

Sound

Submarine navigation

Synthetic aperture sonar

Towed array sonar

Underwater acoustics

Upward looking sonar

References

Bibliography

Further reading

Canada: Stable Sonics, Time Magazine, October 28, 1946. An interesting account of the 4,800 ASDIC sonar devices secretly manufactured at Casa Loma, Toronto, during World War II. Retrieved 25 Sept. 2009.

"Radar of the Deep - SONAR", November 1945, ''Popular Science'' one of the best general public articles on the subject

External links

Sonar Tutorial for Robots

Sonars and the marine environment by Norwegian Defence Research Establishment (FFI)

Single Beam Sonars

Category:Navigational equipment Category:Acronyms Category:Diving equipment Category:British inventions

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name	The Chemical Brothers
landscape	yes
background	group_or_band
alias	The 237 Turbo Nutters, The Dust Brothers, Chemical Ed & Chemical Tom
origin	London, United Kingdom
genre	Big beat, alternative dance, progressive house, breakbeat, trip hop
years active	1991–present
label	Junior Boy's Own, Astralwerks, Freestyle Dust, Virgin Records, Ultra Records
website	TheChemicalBrothers.com
current members	Tom RowlandsEd Simons
past members	}}

The Chemical Brothers are a Grammy award-winning British electronic music duo comprising Tom Rowlands and Ed Simons. Originating in London in 1991, along with The Prodigy, Fatboy Slim, The Crystal Method and fellow acts, they were pioneers at bringing the big beat electronic dance genre to the forefront of pop culture.

History

Background (1984–1991)

Ed Simons was born in Herne Hill, South London, England, on 9 June 1970 to a barrister mother and a father who was not around much when Simons was growing up. Simons’ two main interests when he was young were aeroplanes and musicals. Simons attended two South London public schools, Alleyn's School and Dulwich College. During his school years, he developed a fondness for rare groove and Hip hop music, having frequented a club called The Mud Club from the age of 14. By the time he left school, his two main musical interests were two Manchester bands, New Order and The Smiths. After finishing school with 11 O levels and three A-levels, he continued on to study History, especially Late Medieval History, at the University of Manchester.

Tom Rowlands, a childhood classmate of Simons', was born on 11 January 1971 in Kingston upon Thames, London. When Rowlands was very young, his family relocated to Henley-on-Thames. He later attended Reading Blue Coat School in Berkshire, during which time he became obsessed with Scotland, developing a fondness for the bagpipes in particular. In his early teens, his interest in music broadened to other genres. Initially, some of his favourites included the ''Oh What a Lovely War'' soundtrack, ''2-Tone'', the nascent Goth genre (Sisters of Mercy, Fields of the Nephilim) and the electro sounds of artists such as Kraftwerk, New Order, Cabaret Voltaire and Heaven 17. He described the first Public Enemy album as the record that probably changed his life, and commented that "Miuzi Weighs a Ton" was one of the most amazing tracks he had ever heard. Rowlands also started collecting hip hop records by artists like Eric B and Schoolly D. Rowlands left school with similar accomplishments to Simons', achieving nine O levels and three A levels. For university, he followed Simons to Manchester primarily to immerse himself in its music scene in general and the Haçienda in particular.

Rowlands was also in a band called Ariel prior to meeting up with Simons. Ariel was formed in London by Rowlands and his friends Brendan Melck and Matt Berry. Their first single was "Sea of Beats". This was essentially a white label, before Philip Brown set up Echo Logik Records, their first promo was Bokadilo (ELR1201), Other songs, released on 12" included "Mustn't Grumble" (ELR1203) and their most well-known, "Rollercoaster" (ELR1202). After a year on Echo Logik they signed to the record label deConstruction. They insisted that they get a female singer and they recruited former Xpansions frontwoman Sally Ann Marsh, and after some disappointing songs like "Let It Slide" (Rowlands would later describe it as "a stinker") the band fell apart. One of the last things Ariel did was the song "T Baby" which was remixed by the pair.

Rowlands and Simons then started to DJ at a club called "Naked Under Leather", in the back of a pub, in 1992 under the alias of "The 237 Turbo Nutters" (named after the number of their house on Dickenson Road in Manchester and a reference to their Blackburn raving days). The pair would play hip hop, techno and house.

The Dust Brothers (1992–1994)

Rowlands and Simons called themselves The Dust Brothers, after the US production duo famous for their work with the Beastie Boys. After a while, they began to run out of suitable instrumental hip hop tracks to use, so they started to make their own. Using a Hitachi hi-fi system, a computer, a sampler and a keyboard, they recorded "Song To The Siren", which sampled This Mortal Coil. "Song To The Siren" was released on their own record label, called "Diamond Records" (after Ed's nickname). In October 1992, they pressed 500 white-label copies and took them to various dance record shops around London, but none would play it, saying that it was too slow (The track played at 111 BPM). They sent a copy to London DJ Andrew Weatherall, who made it a permanent fixture in his DJ sets. Weatherall also signed the band to his Junior Boy's Own label. In May 1993, Junior Boy's Own released 'Song To The Siren'.

Around June 1993, the Dust Brothers did their first remixes. The first was "Packet Of Peace" for Justin Robertson's Lionrock outfit, followed by tracks for Leftfield, Republica and The Sandals. Late in 1993, The Dust Brothers completed work on their ''Fourteenth Century Sky'' EP, released in January 1994. It contained the ground-breaking "Chemical Beats", which epitomized the duo's genre-defining big beat sound, later taken up by Fatboy Slim and many more. The EP also contained "One Too Many Mornings", which for the first time showed the less intense, more chilled-out side of The Dust Brothers. Both "One Too Many Mornings" and "Chemical Beats" would later appear on their debut album. ''Fourteenth Century Sky'' was followed later in 1993 by the ''My Mercury Mouth EP''. "Chemical Beats" was also part of the soundtrack for the first edition of the Wipeout games series, having been featured in ''Wipeout'' for the PlayStation in 1995.

In October 1994, The Dust Brothers became resident DJs at the small, but hugely influential Heavenly Sunday Social Club at the Albany pub in London's Great Portland Street. The likes of Noel Gallagher, Paul Weller, James Dean Bradfield and Tim Burgess were regular visitors. The Dust Brothers were subsequently asked to remix tracks by Manic Street Preachers and The Charlatans, plus Primal Scream's "Jailbird" and The Prodigy's "Voodoo People". These two remixes received television exposure, being playlisted by MTV Europe's "The Party Zone" in 1995. Early in 1994, The Dust Brothers were approached in the club one Sunday by Noel Gallagher, from Oasis, who at the time were becoming one of the most prominent guitar bands in Britain. Gallagher told the duo that he had a Balearic inspired track which he had written, which he would like the Dust Brothers to remix. However, over time, Gallagher changed his mind, and in the end the Brothers did not remix it. The track was "Wonderwall".

In March 1995, The Dust Brothers began their first international tour, which included the United States – where they played with Orbital and Underworld – then a series of European festivals. Also around this time, the original Dust Brothers threatened legal action over the use of their name, and so Rowlands and Simons had to decide on a new name quickly. They decided to then call themselves "The Chemical Brothers" after "Chemical Beats" (Simons' grandmother had suggested they call themselves "The Grit Brothers").

In June 1995, they released their fourth single, the first under their new identity. "Leave Home" was released on Junior Boy's Own, as a preview of the imminent debut album and became the band's first chart hit, peaking at No. 17. It stayed at number 17 for 8 weeks, the most weeks a record has stayed at the same place in the charts (apart from Number 1's).

''Exit Planet Dust'' (1995–1996)

In July 1995, The Chemical Brothers released their debut album ''Exit Planet Dust'' (the title inspired by their name change) on Freestyle Dust/Junior Boy's Own. It entered the UK charts at #9 and featured guest vocalist Beth Orton on the song "Alive Alone". It eventually went on to sell over a million copies worldwide, and was used on the soundtrack of the science fiction TV series pilot Virtuality. Shortly after its release, The Chemical Brothers signed to Virgin Records, to which they took their own offshoot label, Freestyle Dust. For their next single, in September 1995, they again used a guest vocalist, for the release of "Life Is Sweet", featuring their friend Tim Burgess, singer with The Charlatans. It reached #25 in the singles charts. The single was also ''Select'' Magazine's Single Of The Month for October. The release included a Daft Punk remix of "Life Is Sweet".

In August 1995, the Chemical Brothers DJ'ed for Oasis at a Sheffield gig. The gig began to backfire when it became apparent that Liam Gallagher didn't seem to like any of the tracks they were spinning. The closest that they could come to pleasing him was the Happy Mondays' "Wrote For Luck". Gallagher proceeded to kick the Chemical Brothers off the turntables and procured a friend from The Verve to continue to DJ. He subsequently favoured psychedelic material to the displeasure of the crowd.

Around this period, The Stone Roses asked the Chemical Brothers to remix "Begging You", from their ''Second Coming'' album. After beginning work on a remix which they viewed as having potential, the Stone Roses changed their minds and the project was cancelled.

In October 1995, the duo returned to the Heavenly Sunday Social for a second and final run of DJ dates. They then became residents at the Heavenly Social on Saturdays at Turnmills. In November, The Chemical Brothers played the Astoria Theatre in London. At this time the Chems usually used a fusion of "Chemical Beats" and The Beatles' "Tomorrow Never Knows" as their encore. During the encore, however, Keith Flint from The Prodigy jumped up on stage to dance, wearing a t-shirt sporting the slogan "Occupation: mad bastard". A few from the crowd subsequently joined in. This resulted in a power cable being kicked loose, bringing the show to a temporary close. The Chemical Brothers confessed to not being too bothered; "because he's Keith from the Prodigy, and he can do whatever the fucking hell he likes" Rowlands said later. Just before Christmas, 1995, they played their biggest gig to date, with The Prodigy, at the Brixton Academy.

In January 1996, ''Exit Planet Dust'' went gold. The Chemical Brothers released their first new material in six months on Virgin, the "Loops Of Fury" EP. The four-track release was limited to 20,000 copies, but is now available for digital download. It entered the UK charts at #13. NME described the lead track as "splashing waves of synths across hard-hitting beats". The EP also contained a Dave Clarke remix of "Chemical Beats", and two other new tracks "Get Up On It Like This" and "(The Best Part Of) Breaking Up".

In February 1996, Select Magazine published a list of the 100 best albums of the 1990s thus far. ''Exit Planet Dust'' was listed at Number 39. In August 1996, The Chemical Brothers supported Oasis at Knebworth, where 125,000 people attended each of the two shows.

During the 1995 Glastonbury Festival, Rowlands and Simons had another conversation with Noel Gallagher. Gallagher told them how much he liked ''Exit Planet Dust'', and asked if he could sing on a future track, similar to the way Tim Burgess had worked on "Life Is Sweet". They didn't think much of the offer at the time, given how busy Gallagher would be with the release of Oasis' ''(What's the Story) Morning Glory?'', plus the complexities of dealing with each others' record companies. However, the duo later worked on a track which they thought would benefit from having a vocal on it. They sent Gallagher a tape of what they had done so far. He worked on it overnight, and left a message with them early the next morning that he was ready to record it. The track was called "Setting Sun" and was finally released in October 1996. It entered the UK charts at the top, giving the duo their first ever Number One single. "Setting Sun" was backed by a longer instrumental version, and also a new track "Buzz Tracks", which was not much more than a DJ tool. The three remaining Beatles' lawyers later wrote to the Chemical Brothers, mistakenly claiming that they had sampled "Tomorrow Never Knows". Virgin Records hired a musicologist to prove that they did not sample the classic 1960s psychedelic song.

Meanwhile, in 1996, ''Live at the Social Volume 1'' was released by Heavenly Records, which became The Chemical Brothers' first mix CD (excluding ''Xmas Dust Up'', a free album that came in a 1994 issue of NME). It was also the duo's first live album, and their only live album (excluding the EP ''Live 05'').

''Dig Your Own Hole'' (1997–1998)

In March 1997, the Brothers released the second track from their forthcoming album, to give the world a further taste of what to expect. "Block Rockin' Beats" went straight to #1 in the UK, possibly thanks, this time, to its Schoolly D vocal sample and re-working of the bassline from 23 Skidoo's single "Coup". The NME named it Single Of The Week and said "It throbs like your head might if you had just done a length underwater in a swimming pool full of amyl." It later won them a Grammy Award for Best Rock Instrumental Performance.

In the US at this time, "Setting Sun" was sitting at Number 80 in the Billboard Top 100, after selling around 80,000 copies, an uncommon achievement for a European "dance" act. Sales from ''Exit Planet Dust'' were also around 150,000.

On 7 April 1997 the Chemical Brothers released their second album, ''Dig Your Own Hole''. It was recorded at the band's own south London studio, with the title taken from graffiti on the wall outside. The album was well received, ''Mixmag'' rating it 10/10 and calling it "mad enough to be thrilling, slick enough for not even remotely trendy coffee tables".

During the summer of 1997, the Brothers toured extensively, particularly in the States. They also became residents at Tokyo's Liquid Rooms. In August, the Chemical Brothers achieved rapprochement with the US Dust Brothers, and asked them to remix the forthcoming single "Elektrobank". They themselves also became highly sought-after for remixes for other artists. Metallica asked the Brothers several times to remix "Enter Sandman", but were repeatedly turned down. In September, the next single from ''Dig Your Own Hole'', "Elektrobank" was released. In November, the pair played at Dublin's Point Theatre, with support from Carl Cox. They also began a US tour in Detroit.

At the end of the year, ''Dig Your Own Hole'''s final track, the nine minute-long "The Private Psychedelic Reel" gave rise to a limited-edition mini-EP of the same name. The b-side consisted of a live version of "Setting Sun", recorded at the Lowlands Festival, Netherlands on 24 August 1997. Also in December, following four sold-out US shows, The Chemical Brothers toured the UK, finishing with a sold-out gig at London's Brixton Academy.

In 1998, they concentrated more on DJ'ing, although some remixes did see the light of day, including "I Think I'm In Love" from Spiritualized. Both a vocal remix and an instrumental remix were included in the single release. Each came in at over seven-and-a-half minutes. Another remix completed by the Brothers was "Delta Sun Bottleneck Stomp", from Mercury Rev. This was another extension in the association between the two bands, since Mercury Rev's Jonathon Donahue contributed to "The Private Psychedelic Reel" on ''Dig Your Own Hole''.

In September 1998, a second mix album, ''Brothers Gonna Work It Out'', was released. It contains some of their own tracks and remixes, as well as songs from artists who have influenced their sound, such as Renegade Soundwave, Meat Beat Manifesto, Carlos "After Dark" Berrios, and Kenny 'Dope' Gonzales.

In May 1999, The Chemical Brothers played three UK dates in Manchester, Sheffield and Brighton, their first since December 1997. Also that month, they released their first new original material in two years, a track called "Hey Boy, Hey Girl". This was more house influenced than hip-hop. In interviews at the time, Rowlands and Simons indicated that the track was inspired by nights out at Sheffield club "Gatecrasher". The track was also one of their more commercially accessible tracks and went to number 3 in the UK charts.

''Surrender'' (1999)

The third album ''Surrender'' was released in June 1999. It featured vocals from Noel Gallagher, Mercury Rev's Jonathan Donahue and Mazzy Star's Hope Sandoval. As "Hey Boy, Hey Girl" had suggested, the album was more house-oriented than the previous two. On one of the album's stand out tracks, "Out Of Control", New Order's Bernard Sumner supported by Primal Scream's Bobby Gillespie provided vocals. It reached Number 1 in the UK album charts, and was widely praised in the print media. The Michel Gondry-directed music video for "Let Forever Be", which utilized ground-breaking video and film effects in its depiction of a young woman's nightmares, also received a lot of attention.

Later that summer, The Brothers headlined the Glastonbury dance tent on the Friday night, followed by a UK tour which ended in December and included Homelands Scotland on 4 September. In November, "Out Of Control", featuring Sumner and Gillespie on vocals, was released as a single. The release also contained the Sasha remix. The final single from ''Surrender'', in February 2000, was the five track "Music: Response" EP, containing the title track and two remixes, plus Electronic Battle Weapon 4 named "Freak of the Week", and a track called "Enjoyed", which was essentially a remix of "Out Of Control" by the Brothers themselves.

A CD copy of ''Surrender'' was placed in the third ''Blue Peter'' time capsule, buried in January 2000. That same month, they appeared on Primal Scream's album ''Xtrmntr'' at track 11 with a remix.

''Come with Us'' (2000–2003)

In June 2000, Tom and Ed played the Pyramid stage at the Glastonbury Festival pulling in the largest audience ever seen in the Festival's history. In August 2000 they played to a large crowd at the main stage at Creamfields festival, Ireland. In December 2000, The Chemical Brothers aired one of their new tracks, "It Began in Afrika" at their New York DJ gigs, supporting U2.

In 2001, they were quite active with releases and live performances. Early in the year, they began working on a fourth album, provisionally titled "Chemical Four". The first track which fans got a taste of was "It Began In Afrika", as previously played in their DJ set in New York. The track would make its live debut in California in April 2001, at the Coachella Valley Music and Arts Festival. Another new track also got its public debut at Coachella, "Galaxy Bounce". As had become customary for their releases and experiments, "It Began In Afrika" was first pressed as a promo, as part of the "Electronic Battle Weapon" series. It received much airplay on dance music radio shows in the UK, and became more and more popular in clubs over the course of the summer. It also became one of the "anthems" in Ibiza as the summer progressed. It was given a full commercial single release in September, reaching #8 in the UK singles chart, even though no promotional video was made for the track.

Rowlands and Simons also remixed a track from Fatboy Slim's ''Halfway Between the Gutter and the Stars'', entitled "Song For Shelter." This remix was released as a single on 3 September 2001 (one week before "It Began in Afrika") as the CD2 single for "Song for Shelter / Ya Mama". It reached #30 in the UK Singles Charts (sales were combined with the CD1 single).

The Chemical Brothers finished work on another album, ''Come with Us'', in October 2001. It featured collaborations with Richard Ashcroft ("The Test"), of The Verve, and long-time collaborator Beth Orton ("The State We're In"). The album was released in January 2002, preceded by a single, "Star Guitar", a melodic, Balearic Beat number, with a promotional video by Michel Gondry that featured passing scenery synchronized to the beat viewed through a train window. What would be the second track on the album, "It Began in Afrika", was released 10 September 2001 to be circulated around the clubbing scene where it was a popular hit. "Star Guitar" was also released as a DVD single, the pair's first.

The album, ''Come with Us'', was less well received than their previous albums, but nonetheless went straight in at #1 in the UK album charts in the first week of its release, selling 100,000 copies. In April, the title track from the album was released as a single with remixes by Fatboy Slim as part of a double-A sided release with "The Test".

During the summer of 2002, The Chemical Brothers traveled the festival circuit to promote the album. Later in 2002, they released two EPs, one specifically aimed at Japan and the other the US (entitled ''AmericanEP''). Both contained remixes, live versions and B-sides. Additionally, the band produced New Order's final non-album single "Here to Stay" and remixed the song as well.

One of their other major songs from this album was "Galaxy Bounce", which was popular and featured as the main title music for the Xbox game ''Project Gotham Racing'', it was also included on the soundtrack for the movie adaptation of Tomb Raider. "Star Guitar" was featured as a song on the PSP's Lumines II.

Two other songs, "Come with Us (Introduction)" and "Star Guitar (Title Screen)", were featured on a ''PS2'' racing game title ''WRC II: Extreme''. Both songs are instrumental.

The Song ''My Elastic Eye'' from the "Come With Us" album was played in the 2004 movie The Butterfly Effect'''' starring Ashton Kutcher and Amy Smart.

Late 2002 and early 2003, saw Rowlands and Simons back in the studio, working on new material, including "The Golden Path", a collaboration with Wayne Coyne, the lead singer of The Flaming Lips. This was released in September 2003, at the same time as a "best of" album, entitled ''Singles 93-03'' marking ten years of The Chemical Brothers' releases. ''Singles 93-03'' included most, but not all, of their singles. A second new track, in addition to "The Golden Path", was included on the album, called "Get Yourself High". ''Singles 93-03'' was also released on DVD, whose extra features included selected live performances and interviews with Rowlands, Simons and many of their collaborators from throughout the period. "Get Yourself High", which featured Canadian rapper k-os on vocals, was released as a single in November 2003.

In late 2003 and 2004, The Chemical Brothers continued to work in the studio, on new material and a remix of "Slow" by Kylie Minogue. After being released on rare white label vinyl, it was subsequently given a commercial release in March on CD (on her next single "Red Blooded Woman") and on exclusive 12" vinyl picture disc (containing two other Kylie remixes). In Summer 2004 they returned to the festival circuit, including appearances at the Glastonbury Festival, Tokyo, Scotland and Ireland. They also visited South America for the second time (being the first time in 1999), arriving at Chile, Argentina and Brazil. It was during these sets that they played new material, including "Acid Children", which proved to be one of the most popular new tracks.

In September 2004 The Chemical Brothers released the "seventh Electronic Battle Weapon". "Electronic Battle Weapon 7" was being released as a one-sided promo-only 12", containing "Acid Children". A marked departure from the Chemical Brothers' previous musical endeavours, it featured a screeching 303 bassline and a distinctive vocal sample; a pitch-altered vocal sample proclaiming "You Are All My Children Now!", which is lifted from an old horror film, A Nightmare on Elm Street Part 2: Freddy's Revenge. It was coupled with the projection of a sinister clown mouthing these same words at their live gigs.

The Electronic Battle Weapon series of promo releases have typically been newly recorded Chemical Brothers tracks, released on promo to allow DJs to test them in a club environment, and to gauge their popularity.

''Push the Button'' (2004–2006)

In 2004, The Chemical Brothers began work on ''Push the Button'', their fifth studio album, which features collaborations with Tim Burgess, Kele Okereke and Anwar Superstar, amongst others. The album was released on 24 January 2005.

"Galvanize", which features Q-Tip on vocals, was the first single to be taken from ''Push the Button'', and premiered exclusively on iTunes. The single was released on 17 January 2005, and entered the UK chart at #3. The second single "Believe" (featuring Kele Okereke from Bloc Party) failed to crack top 10, but still made it into the top 20, peaking at #18. "The Boxer", featuring Tim Burgess, became the duo's first single to fail to crack the top 40.

The album and single "Galvanize" won a Grammy in the Grammy Awards of 2006. One of the songs in this album, "The Big Jump" appears in the video game ''Burnout Revenge'', as well as ''Project Gotham Racing 3''. The track "Surface To Air" features a pulsing chord progression and bassline reminiscent of the intro to The Strokes song "The Modern Age".

An unofficial, remixed version of the album entitled "Flip the Switch" was released as a free download, along with the "Believe EP", six further remixes of "Believe".

In September 2006, the Chemical Brothers were revealed as the first musicians to be involved in Tate Tracks. Tate Modern invited various groups and songwriters to choose a work that inspired them from the gallery's collection of modern art and then write a track about it. The Chemical Brothers' submission, ''Rock Drill'', was inspired by the Jacob Epstein sculpture ''Torso in Metal from The Rock Drill'', and can be heard on headphones in front of the work in the gallery. From October 2006, it also became available to hear online at the Tate Tracks website.

''We Are the Night'' (2007–2009)

The Chemicals welcomed June 2006 with an announcement on their official forum stating that the duo had been working on fresh material, specifically an album, codenamed 'Chemical 6'. Simons also told everyone that the band would be playing select venues in the Summer 2007 season, specifying Rome, and also fabric in London. Simons is also quoted as saying that the duo are 'hoping to put a battle weapon out for the summer,', retrieved possibly referring to the 'Electronic Battle Weapon' series, which are somewhat experimental tracks the band occasionally release on white label.

Electronic Battle Weapon 8 & 9 were debuted on Pete Tong's BBC Radio 1 show on 8 December 2006. The double sided vinyl was finally released just before The Chemical Brother's much anticipated New Year's Eve gig at the famous Turnmills in London. The vinyl had a limited edition release worldwide and has been received well by fans, DJs and critics alike. Electronic Battle Weapon 8 at about six and a half minutes is very distinct from the 'big acid' style that the earlier battle weapons adhered to. It is characterised by 'thundering dirty drums' with a rising synth line, and to many it is perceived as being one of the most euphoric tracks that the Chemicals have released. A version of this track features on the ''We Are The Night'' album and is entitled 'Saturate'. Electronic Battle Weapon 9 is typical Chemicals dancefloor track with their trademark vocoder vocals coupled with sirens and a basic 'tribal' melody.

At the same Turnmills gig, the Brothers also played a previously unreleased song at midnight to welcome 2007 which went down well with the crowd. This track eventually emerged as Burst Generator, found on the album ''We Are The Night''. Many are left wondering if the latest in the Electronic Battle Weapon series were simply one off genius pieces or signal a new direction they could take with the new album, perhaps swaying from their genre defining 'big beat' psychedelic albums of the past. The song was also the band's 100th released song.

On 21 March 2007, The Chemical Brothers officially announced their forthcoming album on MySpace. The new album entitled ''We Are the Night'', was released on 2 July 2007 in the United Kingdom and 17 July 2007 in the United States. The Chemicals cited a delay in the production of artwork for this delay. EMI subsequently released an online 'old-skool' The Chemical Brothers computer game as an apology. The track listing was released to the fans on the official mailing list on 10 April. The new album is heavily collaborated with the likes of Klaxons (on "All Rights Reversed"), Midlake (on "The Pills Won't Help You Now"), Ali Love (on "Do It Again") and Willy Mason (on "Battle Scars").

On 12 April 2007, Pete Tong again had the privilege of giving the world the very first preview of a Chemicals track. This time it was the first single "Do It Again" off their new album, aired on his BBC Radio 1 "In New Music We Trust" show. . The track is widely regarded as dance floor friendly, dominated by pop vocals and a minimalistic production approach. The track is regarded as a 'grower' after gaining mixed reviews after the first listen on Pete Tong's show, with its simplistic catchy vocals and electro beat. The official release of the single was 4 June (digital download) and 14 June (12", 7" and CD). The album went on general release in the UK on 2 July.

In September 2007, The Chemical Brothers played a free live gig in Trafalgar Square as part of the Becks Fusions event. All who attended were provided with 3D glasses to view the on-screen visual effects.

In 2008, The Chemical Brothers' music will also be featured in a movie adaption of Irvine Welsh's best-selling novel Ecstasy: Three Tales of Chemical Romance.

The Chemical Brothers supplied a new track for the Heroes Soundtrack titled "Keep My Composure".

''Further'' and motion picture soundtracks (2010–present)

On 30 March 2010, the band announced on their website that their seventh studio album will be titled ''Further'' and will be released 22 June, adding that it will be "the band's first to be released with corresponding films made specifically to match each of the 8 audio tracks." The films have been made with long-time visuals collaborators Adam Smith and Marcus Lyall. The album has been described as their most "psychedelic and melodic to date". Before the release of the album, the band played four shows in May at the London Roundhouse where they played the album and its accompanying films in its entirety. The films will feature on a special edition DVD and on the iTunes LP edition.

Most reviews have been positive with BBC Music declaring that '...Synths are brutally manhandled and pushed to their limits across the eight tracks' with Ian Wade summarising that 'It’s better to continuously explode than fade away, or something. Really rather wonderful indeed...' The Irish Times also reported that 'This is a very impressive collection that is carried along with a stirring sense of velocity and momentum'. However, praise hasn't been unanimous for the LP, with the American rock magazine Spin giving it a rating of three out of five stars.

At the New York Comic Con, on 10 October 2010, English film director Joe Wright announced that the Chemical Brothers would be scoring the soundtrack to his upcoming film, ''Hanna''. Joe Wright, who had worked with the Chemical Brothers in the past as a member of the visual company Vegetable Vision, expressed his feelings on the score, stating that he was "very excited to finally... work with a more modern beat. There's a lot of bass, it's very loud." The soundtrack was released exclusively on iTunes on 15 March 2011. It will be released on CD on 4 July 2011.

Two weeks after the announcement regarding ''Hanna'', rumors began circulating that the Chemical Brothers had recorded part of the score for the movie ''Black Swan'', after a post in Ed Simon's twitter account. A second post on the Chemical Brothers own twitter account seemed to confirm this. On 22 November 2010, a ''Black Swan'' music video was released along with the movie trailer. This music video featured a different version of the track "Don't Think" and announced that the movie would feature new music from the Chemical Brothers, along with a handful of other artists. The next day, the names of the eight tracks not composed by Clint Mansell – ''Black Swan'''s main composer – were released, listing the Chemical Brothers as contributing three new songs for the movie. On 29 November, an exclusive video was posted on rollingstone.com, containing more footage of the alternate version of "Don't Think". Mansell's work was released the next day. No announcement has been made yet on whether the original tracks not by Mansell would be given a release or not.

Live

The Chemical Brothers are credited as being one of the few truly arena-sized electronic acts. Their live acts comprise large screens displaying psychedelic images, strobe lights and lasers that project over the crowd. There has been speculation over how much of their live gigs are pre-recorded, although they insist (on their official website FAQ) that they have a mere outline of track order and the rest is mixed live. This would seem to be confirmed by concertgoers who have seen gigs on consecutive nights and have posted notable differences between the sets played.

The Brothers have also played at many major festivals, from Glastonbury to the Reading, the HFStival, and Leeds festival. They currently hold the record for most gigs performed in a year at the Brixton Academy. The brothers have infamously, despite their high status in the mainstream, never appeared on Top of the Pops, with the use of music videos to replace the performance, sometimes accompanied by a video apologising for their absence. In 1999, a live US tour video of "Hey Boy, Hey Girl" was shown, even though the song was not in the top 40 at the time, and also released other singles before then at the time.

In addition to performing their own music they also hold regular DJ nights where they mix other artist's tracks (in the style of ''Brothers Gonna Work It Out'').

As with their recorded albums, the Chemical Brothers are well known for their incorporation of guest vocalists into their live performances. Notable appearances in recent gigs have included Bernard Sumner of New Order, who sang on the original "Out of Control", Wayne Coyne of The Flaming Lips, and Tim Burgess.

The duo also played at the launch event for the Wii video game console.

On the night of 1 September 2007, the Chemical Brothers played at the main stage of the Electric Picnic to a crowd of around 20,000. The Chemical Brothers appeared in Los Angeles on 29 September 2007, headlining the 13th Annual Nocturnal Wonderland Festival.

The duo was one of the head-liners for Roskilde Festival 2008 in Denmark. The festival is held from the 3rd-6 July and is the biggest festival in Northern Europe.

The Chemical Brothers played at London's Olympia Grand Hall on 30 August 2008. This was the first time any major band has played at Olympia's Grand Hall in over 10 years.

On 18 April 2009, the Chemical Brothers performed a DJ Set at the Coachella Festival, at which they premiered two previously unnamed new tracks. The tracks were the bonus track "Don't Think", and "Escape Velocity", both of which were later included on the album ''Further''.

On 8 February 2010, they confirmed their presence at Sónar Festival in Barcelona in June 2010. They also announced they would be performing another two nights at the London Roundhouse in Camden, on 20 and 21 May. Due to phenomenal demand, as tickets sold out within two minutes, they added a further two nights; 22 and 23 May.

On 3 September 2010, they performed at North Coast Music Festival in Chicago. The following day they performed at Electric Zoo festival in New York City.

4–14 March 2011, they headlined the Future Music Festival in 5 cities across Australia.

On 27 March 2011, they headlined Ultra Music Festival in Miami, FL and closed out the Main Stage for the weekend. They also were the closing performance at the Coachella Valley Music and Arts Festival Friday 15 April 2011. The Chemical Brothers will headline the UK dance festival Creamfields in Cheshire on 27 August 2011.

The band also played at the 'Other Stage' at Glastonbury Festival 2011 as that stage's lead headliners.

Logo

The typeface used to write the typical "The Chemical Brothers" logo is derived from Sho, designed by Karlgeorg Hoefer in 1992. The Chemical Brothers' original logo differs only in a few details from orthodox Sho, e.g. in the letters a and b. Mergenthaler Linotype Company holds the licence for this typeface.

Discography

Studio albums

''Exit Planet Dust'' (1995)

''Dig Your Own Hole'' (1997)

''Surrender'' (1999)

''Come with Us'' (2002)

''Push the Button'' (2005)

''We Are the Night'' (2007)

''Further'' (2010)

Soundtrack albums

''Hanna'' (2011)

Main compilation albums

''Brothers Gonna Work It Out'' (1998)

''Singles 93-03'' (2003)

''Brotherhood'' (2008)

See also

Daft Punk

Fatboy Slim

Orbital

The Prodigy

References

External links

YouTube Remix Channel (Taiwan)

Category:British electronic music groups Category:British techno music groups Category:English dance music groups Category:English house music groups Category:Musical groups established in 1991 Category:1991 establishments in England Category:Club DJs Category:Remixers Category:Virgin Records artists Category:Astralwerks artists Category:Musical groups from Manchester Category:Celebrity duos Category:Breakbeat musicians Category:Electronic music duos Category:BRIT Award winners Category:Grammy Award winners Category:People educated at Alleyn's School

ca:The Chemical Brothers cs:The Chemical Brothers da:The Chemical Brothers de:The Chemical Brothers es:The Chemical Brothers fr:The Chemical Brothers ko:케미컬 브라더스 it:The Chemical Brothers ka:The Chemical Brothers lv:The Chemical Brothers lt:The Chemical Brothers hu:The Chemical Brothers mk:The Chemical Brothers nl:The Chemical Brothers ja:ケミカル・ブラザーズ no:The Chemical Brothers pl:The Chemical Brothers pt:The Chemical Brothers ro:The Chemical Brothers ru:The Chemical Brothers simple:The Chemical Brothers sk:The Chemical Brothers fi:The Chemical Brothers sv:The Chemical Brothers th:เดอะเคมิคอลบราเทอร์ส tr:The Chemical Brothers uk:The Chemical Brothers zh:化學兄弟

Name	Jeff Mills
Background	non_performing_personnel
Birth name	Jeff Mills
Born	June 18, 1963Detroit, Michigan, U.S.
Instrument	Turntables
Genre	Techno
Occupation	Disc jockey
Label	Axis Records
Past members	}}

Jeff Mills (born 18 June 1963 in Detroit, Michigan) is an American techno DJ and producer.

Career

Starting in the early 1980s, Mills, using the name "The Wizard", was a recurring guest DJ on "The Electrifying Mojo" radio show on WJLB. He performed DJ tricks like beat juggling and scratching during his sets, some of which were pre-recorded.

Mills and former Parliament bass player 'Mad' Mike Banks were founding members of Detroit techno collective Underground Resistance (UR), which embraced revolutionary rhetoric and only appeared in public dressed in ski masks and black combat suits.

Mills never officially left UR, but did relocate from Detroit, first to New York, then Berlin (as a resident at the Tresor club), and then Chicago. There in 1992, with fellow Detroit native Robert Hood, he set up the record label Axis, and later, sub-labels Purpose Maker, Tomorrow, and 6277, all aiming for a more minimal sound than most of the techno being produced in those years.

In his DJ sets, Mills usually uses three decks, a Roland 909 drum-machine, and up to seventy records in one hour. Mills' ''Exhibitionist'' DVD, from 2004, features him mixing live on three decks and CD player in a studio.

Releases

Albums

1992 Waveform Transmission - Volume 1

1994 Waveform Transmission - Volume 3

1996 Mix-Up Volume 2 Live at the Liquid Room (a live DJ set)

1996 Purpose Maker Compilation

1997 The other Day

1999 From the 21st

2000 Every Dog Has Its Day

2000 Metropolis (soundtrack to the Fritz Lang film)

2000 The Art of Connecting

2000 Lifelike

2002 Actual

2002 At First Sight

2004 Exhibitionist (a live DJ set, also available as a DVD)

2004 Choice: A Collection of Classics

2005 The Three Ages (new soundtrack to the Buster Keaton film)

2005 Contact Special

The Mission Objective (2005) (a live DJ set)

2006 Blue Potential

2007 One Man Spaceship

2008 Gamma Player Compilation Vol 1: The Universe By Night

2009 Sleeper Wakes

2010 The Occurrence

2011 The Power

2011 2087

Axis

AX-001 - Tranquilizer

AX-004 - Mecca

AX-005 - Thera

AX-006 - More Drama

AX-008 - Cycle 30

AX-009ab - AX-009 Series

AX-009 cd - Actual

AX-009ef - Medium

AX-010 - Growth

AX-011 - Purpose Maker EP

AX-012 - Humana

AX-013 - Tephra

AX-015 - Other Day EP

AX-016 - Very (first released vinyls were perfume-scented to 'enhance the idea of influence through interaction)

AX-018 - Tomorrow EP

AX-019 - Apollo

AX-019 OUR - From the 21st part 1

AX-019 AFV - From the 21st part 2

AX-020 - Every Dog has its Day vol. 1

AX-021 - Lifelike EP

AX-022 - Metropolis

AX-023 - Every Dog has its Day vol. 2

AX-024 - 4Art/UFO

AX-026 - Every Dog has its Day vol. 3

AX-030 - Every Dog has its Day vol. 4

AX-036 - See the Light Part 1

AX-037 - See the Light Part 2

AX-038 - See the Light Part 3

AX-039 - Expanded

AX-040 - The Tomorrow Time Forgot

AX-041 - Suspense/Dramatized

AX-043 - Time Mechanic

AX-044 - Blade Runner (EP) (inspired by the Ridley Scott film)

AX-048 - Systematic/The Sin

AX-049 - Alpha Centauri

AX-052 - Flyby - X-102

AX-055 - The Good Robot (Coming Soon)

Purpose Maker

PM-001 - Java

PM-002 - Kat Moda

PM-003 - Force Universelle

PM-004 - Our Man in Havanna

PM-005 - Steampit

PM-006 - Vanishing Act

PM-007 - Live Series

PM-008 - Skin Deep

PM-009 - If/Tango

PM-010 - Circus

PM-012 - Jetset

PM-014 - Electrical Experience

PM-015 - Divine

PM-016 - Kana

PM-020 - The Bells [10th Anniversary]

PM-021 - Natural World

PMWCD9601 - Purpose Maker Compilation [CD]

PMWLP9601 - Purpose Maker Compilation [2xLP]

Tomorrow

TW-001 - Preview EP

TW-300 - Sculptures 1-3 CD

TW-400 - Europa CD

TW-800 - Time Machines CD

6277

MISSION 01 Elektrabel - Elektrabel EP 2003

MISSION 02 Hieroglyphic Being - Du Commencement A L'Eternite 2004

MISSION 03 Elektrabel - Crocks EP 2005

MISSION 04 Elektrabel - For Various Reasons 2005

MISSION 05 Sub Space - First Step EP 2005

MISSION 06 Zachary Lubin - Controllability 2005

MISSION 07 Various artists (Jeff Mills Mix) - The objective Mission [Top Secret] 2005

MISSION 08 Trefa - Elektrabel 2006

MISSION 09 Ben Gibson - No Signify EP 2006

MISSION 10 CounterPart - The Martian Mystique 2006

MISSION 11 Johannes Volk - The Mysteries Of Tharsis Montes 2006

MISSION 12 Jeroen - New Reality

Tresor Records

Waveform Transmission Vol. 1

The Extremist

Waveform Transmission Vol. 3

Waveform Transmission Vol. 3 (Detroit Cut)

Atlantis (under moniker X-103)

References

External links

Jeff Mills discography at Discogs.

See Deep House Page for some very rare live Chicago sets from around 1985-86.

Higher Frequency Interview

Hardware Interview

La Sauterelle = Musiques electroniques : house, techno, electro

''Real Detroit Weekly'' Interview

Category:1963 births Category:Living people Category:African American musicians Category:American expatriates in Germany Category:American techno musicians Category:American DJs Category:Musicians from Detroit, Michigan

bg:Джеф Милс de:Jeff Mills es:Jeff Mills fr:Jeff Mills it:Jeff Mills hu:Jeff Mills nl:Jeff Mills ja:ジェフ・ミルズ pl:Jeff Mills ru:Миллз, Джефф fi:Jeff Mills sv:Jeff Mills