A Neumann U87 condenser microphone with shock mount

A Sennheiser microphone

A microphone (colloquially called a mic or mike; both pronounced /ˈmaɪk/)^[1] is an acoustic-to-electric transducer or sensor that converts sound into an electrical signal. Microphones are used in many applications such as telephones, tape recorders, karaoke systems, hearing aids, motion picture production, live and recorded audio engineering, FRS radios, megaphones, in radio and television broadcasting and in computers for recording voice, speech recognition, VoIP, and for non-acoustic purposes such as ultrasonic checking or knock sensors.

Most microphones today use electromagnetic induction (dynamic microphone), capacitance change (condenser microphone), piezoelectric generation, or light modulation to produce an electrical voltage signal from mechanical vibration.

History[link]

This section requires expansion.

Both Thomas Alva Edison and Emile Berliner filed patent applications for the carbon microphone, in March and June 1877 respectively. After a long legal battle, Edison emerged the victor, and the Berliner patent was ruled invalid by both American and British courts.

Components[link]

The sensitive transducer element of a microphone is called its element or capsule. A complete microphone also includes a housing, some means of bringing the signal from the element to other equipment, and often an electronic circuit to adapt the output of the capsule to the equipment being driven. A wireless microphone contains a radio transmitter.

Varieties[link]

Microphones are referred to by their transducer principle, such as condenser, dynamic, etc., and by their directional characteristics. Sometimes other characteristics such as diaphragm size, intended use or orientation of the principal sound input to the principal axis (end- or side-address) of the microphone are used to describe the microphone.

[edit] Condenser microphone

Inside the Oktava 319 condenser microphone

The condenser microphone, invented at Bell Labs in 1916 by E. C. Wente^[2] is also called a capacitor microphone or electrostatic microphone — capacitors were historically called condensers. Here, the diaphragm acts as one plate of a capacitor, and the vibrations produce changes in the distance between the plates. There are two types, depending on the method of extracting the audio signal from the transducer: DC-biased and radio frequency (RF) or high frequency (HF) condenser microphones. With a DC-biased microphone, the plates are biased with a fixed charge (Q). The voltage maintained across the capacitor plates changes with the vibrations in the air, according to the capacitance equation (C = ^Q⁄_V), where Q = charge in coulombs, C = capacitance in farads and V = potential difference in volts. The capacitance of the plates is inversely proportional to the distance between them for a parallel-plate capacitor. (See capacitance for details.) The assembly of fixed and movable plates is called an "element" or "capsule".

A nearly constant charge is maintained on the capacitor. As the capacitance changes, the charge across the capacitor does change very slightly, but at audible frequencies it is sensibly constant. The capacitance of the capsule (around 5 to 100 pF) and the value of the bias resistor (100 MΩ to tens of GΩ) form a filter that is high-pass for the audio signal, and low-pass for the bias voltage. Note that the time constant of an RC circuit equals the product of the resistance and capacitance.

Within the time-frame of the capacitance change (as much as 50 ms at 20 Hz audio signal), the charge is practically constant and the voltage across the capacitor changes instantaneously to reflect the change in capacitance. The voltage across the capacitor varies above and below the bias voltage. The voltage difference between the bias and the capacitor is seen across the series resistor. The voltage across the resistor is amplified for performance or recording. In most cases, the electronics in the microphone itself contribute no voltage gain as the voltage differential is quite significant, up to several volts for high sound levels. Since this is a very high impedance circuit, current gain only is usually needed with the voltage remaining constant.

AKG C451B small-diaphragm condenser microphone

RF condenser microphones use a comparatively low RF voltage, generated by a low-noise oscillator. The signal from the oscillator may either be amplitude modulated by the capacitance changes produced by the sound waves moving the capsule diaphragm, or the capsule may be part of a resonant circuit that modulates the frequency of the oscillator signal. Demodulation yields a low-noise audio frequency signal with a very low source impedance. The absence of a high bias voltage permits the use of a diaphragm with looser tension, which may be used to achieve wider frequency response due to higher compliance. The RF biasing process results in a lower electrical impedance capsule, a useful by-product of which is that RF condenser microphones can be operated in damp weather conditions that could create problems in DC-biased microphones with contaminated insulating surfaces. The Sennheiser "MKH" series of microphones use the RF biasing technique.

Condenser microphones span the range from telephone transmitters through inexpensive karaoke microphones to high-fidelity recording microphones. They generally produce a high-quality audio signal and are now the popular choice in laboratory and recording studio applications. The inherent suitability of this technology is due to the very small mass that must be moved by the incident sound wave, unlike other microphone types that require the sound wave to do more work. They require a power source, provided either via microphone inputs on equipment as phantom power or from a small battery. Power is necessary for establishing the capacitor plate voltage, and is also needed to power the microphone electronics (impedance conversion in the case of electret and DC-polarized microphones, demodulation or detection in the case of RF/HF microphones). Condenser microphones are also available with two diaphragms that can be electrically connected to provide a range of polar patterns (see below), such as cardioid, omnidirectional, and figure-eight. It is also possible to vary the pattern continuously with some microphones, for example the Røde NT2000 or CAD M179.

Electret condenser microphone[link]

First patent on foil electret microphone by G. M. Sessler et al. (pages 1 to 3)

An electret microphone is a type of capacitor microphone invented by Gerhard Sessler and Jim West at Bell laboratories in 1962. ^[3] The externally applied charge described above under condenser microphones is replaced by a permanent charge in an electret material. An electret is a ferroelectric material that has been permanently electrically charged or polarized. The name comes from electrostatic and magnet; a static charge is embedded in an electret by alignment of the static charges in the material, much the way a magnet is made by aligning the magnetic domains in a piece of iron.

Due to their good performance and ease of manufacture, hence low cost, the vast majority of microphones made today are electret microphones; a semiconductor manufacturer^[4] estimates annual production at over one billion units. Nearly all cell-phone, computer, PDA and headset microphones are electret types. They are used in many applications, from high-quality recording and lavalier use to built-in microphones in small sound recording devices and telephones. Though electret microphones were once considered low quality, the best ones can now rival traditional condenser microphones in every respect and can even offer the long-term stability and ultra-flat response needed for a measurement microphone. Unlike other capacitor microphones, they require no polarizing voltage, but often contain an integrated preamplifier that does require power (often incorrectly called polarizing power or bias). This preamplifier is frequently phantom powered in sound reinforcement and studio applications. Monophonic microphones designed for personal computer (PC) use, sometimes called multimedia microphones, use a 3.5 mm plug as usually used, without power, for stereo; the ring, instead of carrying the signal for a second channel, carries power via a resistor from (normally) a 5 V supply in the computer. Stereophonic microphones use the same connector; there is no obvious way to determine which standard is used by equipment and microphones.

Only the best electret microphones rival good DC-polarized units in terms of noise level and quality; electret microphones lend themselves to inexpensive mass-production, while inherently expensive non-electret condenser microphones are made to higher quality.

Dynamic microphone[link]

Patti Smith singing into a Shure SM58 (dynamic cardioid type) microphone

Dynamic microphones work via electromagnetic induction. They are robust, relatively inexpensive and resistant to moisture. This, coupled with their potentially high gain before feedback, makes them ideal for on-stage use.

Moving-coil microphones use the same dynamic principle as in a loudspeaker, only reversed. A small movable induction coil, positioned in the magnetic field of a permanent magnet, is attached to the diaphragm. When sound enters through the windscreen of the microphone, the sound wave moves the diaphragm. When the diaphragm vibrates, the coil moves in the magnetic field, producing a varying current in the coil through electromagnetic induction. A single dynamic membrane does not respond linearly to all audio frequencies. Some microphones for this reason utilize multiple membranes for the different parts of the audio spectrum and then combine the resulting signals. Combining the multiple signals correctly is difficult and designs that do this are rare and tend to be expensive. There are on the other hand several designs that are more specifically aimed towards isolated parts of the audio spectrum. The AKG D 112, for example, is designed for bass response rather than treble.^[5] In audio engineering several kinds of microphones are often used at the same time to get the best result.

Ribbon microphone[link]

Edmund Lowe using a ribbon microphone

Ribbon microphones use a thin, usually corrugated metal ribbon suspended in a magnetic field. The ribbon is electrically connected to the microphone's output, and its vibration within the magnetic field generates the electrical signal. Ribbon microphones are similar to moving coil microphones in the sense that both produce sound by means of magnetic induction. Basic ribbon microphones detect sound in a bi-directional (also called figure-eight) pattern because the ribbon, which is open to sound both front and back, responds to the pressure gradient rather than the sound pressure. Though the symmetrical front and rear pickup can be a nuisance in normal stereo recording, the high side rejection can be used to advantage by positioning a ribbon microphone horizontally, for example above cymbals, so that the rear lobe picks up only sound from the cymbals. Crossed figure 8, or Blumlein pair, stereo recording is gaining in popularity, and the figure 8 response of a ribbon microphone is ideal for that application.

Other directional patterns are produced by enclosing one side of the ribbon in an acoustic trap or baffle, allowing sound to reach only one side. The classic RCA Type 77-DX microphone has several externally adjustable positions of the internal baffle, allowing the selection of several response patterns ranging from "Figure-8" to "Unidirectional". Such older ribbon microphones, some of which still provide high quality sound reproduction, were once valued for this reason, but a good low-frequency response could only be obtained when the ribbon was suspended very loosely, which made them relatively fragile. Modern ribbon materials, including new nanomaterials^[6] have now been introduced that eliminate those concerns, and even improve the effective dynamic range of ribbon microphones at low frequencies. Protective wind screens can reduce the danger of damaging a vintage ribbon, and also reduce plosive artifacts in the recording. Properly designed wind screens produce negligible treble attenuation. In common with other classes of dynamic microphone, ribbon microphones don't require phantom power; in fact, this voltage can damage some older ribbon microphones. Some new modern ribbon microphone designs incorporate a preamplifier and, therefore, do require phantom power, and circuits of modern passive ribbon microphones, i.e., those without the aforementioned preamplifier, are specifically designed to resist damage to the ribbon and transformer by phantom power. Also there are new ribbon materials available that are immune to wind blasts and phantom power.

Carbon microphone[link]

A carbon microphone, also known as a carbon button microphone (or sometimes just a button microphone), use a capsule or button containing carbon granules pressed between two metal plates like the Berliner and Edison microphones. A voltage is applied across the metal plates, causing a small current to flow through the carbon. One of the plates, the diaphragm, vibrates in sympathy with incident sound waves, applying a varying pressure to the carbon. The changing pressure deforms the granules, causing the contact area between each pair of adjacent granules to change, and this causes the electrical resistance of the mass of granules to change. The changes in resistance cause a corresponding change in the current flowing through the microphone, producing the electrical signal. Carbon microphones were once commonly used in telephones; they have extremely low-quality sound reproduction and a very limited frequency response range, but are very robust devices. The Boudet microphone, which used relatively large carbon balls, was similar to the granule carbon button microphones.^[7]

Unlike other microphone types, the carbon microphone can also be used as a type of amplifier, using a small amount of sound energy to control a larger amount of electrical energy. Carbon microphones found use as early telephone repeaters, making long distance phone calls possible in the era before vacuum tubes. These repeaters worked by mechanically coupling a magnetic telephone receiver to a carbon microphone: the faint signal from the receiver was transferred to the microphone, with a resulting stronger electrical signal to send down the line. One illustration of this amplifier effect was the oscillation caused by feedback, resulting in an audible squeal from the old "candlestick" telephone if its earphone was placed near the carbon microphone.

Piezoelectric microphone[link]

A crystal microphone or piezo microphone uses the phenomenon of piezoelectricity — the ability of some materials to produce a voltage when subjected to pressure — to convert vibrations into an electrical signal. An example of this is potassium sodium tartrate, which is a piezoelectric crystal that works as a transducer, both as a microphone and as a slimline loudspeaker component. Crystal microphones were once commonly supplied with vacuum tube (valve) equipment, such as domestic tape recorders. Their high output impedance matched the high input impedance (typically about 10 megohms) of the vacuum tube input stage well. They were difficult to match to early transistor equipment, and were quickly supplanted by dynamic microphones for a time, and later small electret condenser devices. The high impedance of the crystal microphone made it very susceptible to handling noise, both from the microphone itself and from the connecting cable.

Piezoelectric transducers are often used as contact microphones to amplify sound from acoustic musical instruments, to sense drum hits, for triggering electronic samples, and to record sound in challenging environments, such as underwater under high pressure. Saddle-mounted pickups on acoustic guitars are generally piezoelectric devices that contact the strings passing over the saddle. This type of microphone is different from magnetic coil pickups commonly visible on typical electric guitars, which use magnetic induction, rather than mechanical coupling, to pick up vibration.

Fiber optic microphone[link]

The Optoacoustics 1140 fiber optic microphone

A fiber optic microphone converts acoustic waves into electrical signals by sensing changes in light intensity, instead of sensing changes in capacitance or magnetic fields as with conventional microphones.^[8][9]

During operation, light from a laser source travels through an optical fiber to illuminate the surface of a reflective diaphragm. Sound vibrations of the diaphragm modulate the intensity of light reflecting off the diaphragm in a specific direction. The modulated light is then transmitted over a second optical fiber to a photo detector, which transforms the intensity-modulated light into analog or digital audio for transmission or recording. Fiber optic microphones possess high dynamic and frequency range, similar to the best high fidelity conventional microphones.

Fiber optic microphones do not react to or influence any electrical, magnetic, electrostatic or radioactive fields (this is called EMI/RFI immunity). The fiber optic microphone design is therefore ideal for use in areas where conventional microphones are ineffective or dangerous, such as inside industrial turbines or in magnetic resonance imaging (MRI) equipment environments.

Fiber optic microphones are robust, resistant to environmental changes in heat and moisture, and can be produced for any directionality or impedance matching. The distance between the microphone's light source and its photo detector may be up to several kilometers without need for any preamplifier or other electrical device, making fiber optic microphones suitable for industrial and surveillance acoustic monitoring.

Fiber optic microphones are used in very specific application areas such as for infrasound monitoring and noise-canceling. They have proven especially useful in medical applications, such as allowing radiologists, staff and patients within the powerful and noisy magnetic field to converse normally, inside the MRI suites as well as in remote control rooms.^[10]) Other uses include industrial equipment monitoring and sensing, audio calibration and measurement, high-fidelity recording and law enforcement.

Laser microphone[link]

Laser microphones are often portrayed in movies as spy gadgets, because they can be used to pick up sound at a distance from the microphone equipment. A laser beam is aimed at the surface of a window or other plane surface that is affected by sound. The vibrations of this surface change the angle at which the beam is reflected, and the motion of the laser spot from the returning beam is detected and converted to an audio signal.

In a more robust and expensive implementation, the returned light is split and fed to an interferometer, which detects movement of the surface by changes in the optical path length of the reflected beam. The former implementation is a tabletop experiment; the latter requires an extremely stable laser and precise optics.

A new type of laser microphone is a device that uses a laser beam and smoke or vapor to detect sound vibrations in free air. On 25 August 2009, U.S. patent 7,580,533 issued for a Particulate Flow Detection Microphone based on a laser-photocell pair with a moving stream of smoke or vapor in the laser beam's path. Sound pressure waves cause disturbances in the smoke that in turn cause variations in the amount of laser light reaching the photo detector. A prototype of the device was demonstrated at the 127th Audio Engineering Society convention in New York City from 9 through 12 October 2009.

Liquid microphone[link]

Early microphones did not produce intelligible speech, until Alexander Graham Bell made improvements including a variable resistance microphone/transmitter. Bell's liquid transmitter consisted of a metal cup filled with water with a small amount of sulfuric acid added. A sound wave caused the diaphragm to move, forcing a needle to move up and down in the water. The electrical resistance between the wire and the cup was then inversely proportional to the size of the water meniscus around the submerged needle. Elisha Gray filed a caveat for a version using a brass rod instead of the needle. Other minor variations and improvements were made to the liquid microphone by Majoranna, Chambers, Vanni, Sykes, and Elisha Gray, and one version was patented by Reginald Fessenden in 1903. These were the first working microphones, but they were not practical for commercial application. The famous first phone conversation between Bell and Watson took place using a liquid microphone.

MEMS microphone[link]

The MEMS (MicroElectrical-Mechanical System) microphone is also called a microphone chip or silicon microphone. The pressure-sensitive diaphragm is etched directly into a silicon chip by MEMS techniques, and is usually accompanied with integrated preamplifier. Most MEMS microphones are variants of the condenser microphone design. Often MEMS microphones have built in analog-to-digital converter (ADC) circuits on the same CMOS chip making the chip a digital microphone and so more readily integrated with modern digital products. Major manufacturers producing MEMS silicon microphones are Wolfson Microelectronics (WM7xxx), Analog Devices, Akustica (AKU200x), Infineon (SMM310 product), Knowles Electronics, Memstech (MSMx), NXP Semiconductors, Sonion MEMS, AAC Acoustic Technologies,^[11] and Omron.^[12]

Speakers as microphones[link]

A loudspeaker, a transducer that turns an electrical signal into sound waves, is the functional opposite of a microphone. Since a conventional speaker is constructed much like a dynamic microphone (with a diaphragm, coil and magnet), speakers can actually work "in reverse" as microphones. The result, though, is a microphone with poor quality, limited frequency response (particularly at the high end), and poor sensitivity. In practical use, speakers are sometimes used as microphones in applications where high quality and sensitivity are not needed such as intercoms, walkie-talkies or Video game voice chat peripherals, or when conventional microphones are in short supply.

However, there is at least one other practical application of this principle: Using a medium-size woofer placed closely in front of a "kick" (bass drum) in a drum set to act as a microphone. The use of relatively large speakers to transduce low frequency sound sources, especially in music production, is becoming fairly common. A product example of this type of device is the Yamaha Subkick, a 6.5-inch (170 mm) woofer shock-mounted into a 10" drum shell used in front of kick drums. Since a relatively massive membrane is unable to transduce high frequencies, placing a speaker in front of a kick drum is often ideal for reducing cymbal and snare bleed into the kick drum sound. Less commonly, microphones themselves can be used as speakers, almost always as tweeters. Microphones, however, are not designed to handle the power that speaker components are routinely required to cope with. One instance of such an application was the STC microphone-derived 4001 super-tweeter, which was successfully used in a number of high quality loudspeaker systems from the late 1960s to the mid-70s.

Capsule design and directivity[link]

The inner elements of a microphone are the primary source of differences in directivity. A pressure microphone uses a diaphragm between a fixed internal volume of air and the environment, and responds uniformly to pressure from all directions, so it is said to be omnidirectional. A pressure-gradient microphone uses a diaphragm that is at least partially open on both sides. The pressure difference between the two sides produces its directional characteristics. Other elements such as the external shape of the microphone and external devices such as interference tubes can also alter a microphone's directional response. A pure pressure-gradient microphone is equally sensitive to sounds arriving from front or back, but insensitive to sounds arriving from the side because sound arriving at the front and back at the same time creates no gradient between the two. The characteristic directional pattern of a pure pressure-gradient microphone is like a figure-8. Other polar patterns are derived by creating a capsule that combines these two effects in different ways. The cardioid, for instance, features a partially closed backside, so its response is a combination of pressure and pressure-gradient characteristics.^[13]

Microphone polar patterns[link]

(Microphone facing top of page in diagram, parallel to page):

• 

  Omnidirectional
• 

  Subcardioid
• 

  Cardioid
• 

  Supercardioid
• 

  Bi-directional or Figure of 8
• 

  Hypercardioid
• 

  Shotgun

A microphone's directionality or polar pattern indicates how sensitive it is to sounds arriving at different angles about its central axis. The polar patterns illustrated above represent the locus of points that produce the same signal level output in the microphone if a given sound pressure level (SPL) is generated from that point. How the physical body of the microphone is oriented relative to the diagrams depends on the microphone design. For large-membrane microphones such as in the Oktava (pictured above), the upward direction in the polar diagram is usually perpendicular to the microphone body, commonly known as "side fire" or "side address". For small diaphragm microphones such as the Shure (also pictured above), it usually extends from the axis of the microphone commonly known as "end fire" or "top/end address".

Some microphone designs combine several principles in creating the desired polar pattern. This ranges from shielding (meaning diffraction/dissipation/absorption) by the housing itself to electronically combining dual membranes.

Omnidirectional[link]

An omnidirectional (or nondirectional) microphone's response is generally considered to be a perfect sphere in three dimensions. In the real world, this is not the case. As with directional microphones, the polar pattern for an "omnidirectional" microphone is a function of frequency. The body of the microphone is not infinitely small and, as a consequence, it tends to get in its own way with respect to sounds arriving from the rear, causing a slight flattening of the polar response. This flattening increases as the diameter of the microphone (assuming it's cylindrical) reaches the wavelength of the frequency in question. Therefore, the smallest diameter microphone gives the best omnidirectional characteristics at high frequencies.

The wavelength of sound at 10 kHz is little over an inch (3.4 cm) so the smallest measuring microphones are often 1/4" (6 mm) in diameter, which practically eliminates directionality even up to the highest frequencies. Omnidirectional microphones, unlike cardioids, do not employ resonant cavities as delays, and so can be considered the "purest" microphones in terms of low coloration; they add very little to the original sound. Being pressure-sensitive they can also have a very flat low-frequency response down to 20 Hz or below. Pressure-sensitive microphones also respond much less to wind noise and plosives than directional (velocity sensitive) microphones.

An example of a nondirectional microphone is the round black eight ball.^[14]

Unidirectional[link]

A unidirectional microphone is sensitive to sounds from only one direction. The diagram above illustrates a number of these patterns. The microphone faces upwards in each diagram. The sound intensity for a particular frequency is plotted for angles radially from 0 to 360°. (Professional diagrams show these scales and include multiple plots at different frequencies. The diagrams given here provide only an overview of typical pattern shapes, and their names.)

Cardioid[link]

US664A University Sound Dynamic Supercardioid Microphone

The most common unidirectional microphone is a cardoid microphone, so named because the sensitivity pattern is a cardoid. The cardoid family of microphones are commonly used as vocal or speech microphones, since they are good at rejecting sounds from other directions. In three dimensions, the cardioid is shaped like an apple centred around the microphone which is the "stalk" of the apple. The cardoid response reduces pickup from the side and rear, helping to avoid feedback from the monitors. Since pressure gradient transducer microphones are directional, putting them very close to the sound source (at distances of a few centimeters) results in a bass boost. This is known as the proximity effect.^[15] The SM58 has been the most commonly used microphone for live vocals for more than 40 years^[16] demonstrating the importance and popularity of cardoid mikes.

A cardioid microphone is effectively a superposition of an omnidirectional and a figure-8 microphone; for sound waves coming from the back, the negative signal from the figure-8 cancels the positive signal from the omnidirectional element, whereas for sound waves coming from the front, the two add to each other. A hyper-cardioid microphone has a tighter area of front sensitivity and a smaller lobe of rear sensitivity. A hypercardioid microphone is similar, but with a slightly larger figure-8 contribution. A super-cardioid microphone is similar to a hyper-cardioid, except there is more front pickup and less rear pickup.

Bi-directional[link]

"Figure 8" or bi-directional microphones receive sound equally from both the front and back of the element. Most ribbon microphones are of this pattern. In principle they do not respond to sound pressure at all, only to the gradient between front and back; since sound arriving from the side reaches front and back equally there is no gradient and therefore no sensitivity to sound from that direction. While omnidirectional microphones are scalar transducers responding to pressure from any direction, bi-directional microphones are vector transducers responding to the gradient along an axis normal to the plane of the diaphragm. As a result, output polarity is inverted for sounds arriving from the back side.

Shotgun[link]

An Audio-Technica shotgun microphone

Shotgun microphones are the most highly directional. They have small lobes of sensitivity to the left, right, and rear but are significantly less sensitive to the side and rear than other directional microphones. This results from placing the element at the back end of a tube with slots cut along the side; wave cancellation eliminates much of the off-axis sound. Due to the narrowness of their sensitivity area, shotgun microphones are commonly used on television and film sets, in stadiums, and for field recording of wildlife.

Boundary or "PZM"[link]

Several approaches have been developed for effectively using a microphone in less-than-ideal acoustic spaces, which often suffer from excessive reflections from one or more of the surfaces (boundaries) that make up the space. If the microphone is placed in, or very close to, one of these boundaries, the reflections from that surface are not sensed by the microphone. Initially this was done by placing an ordinary microphone adjacent to the surface, sometimes in a block of acoustically transparent foam. Sound engineers Ed Long and Ron Wickersham developed the concept of placing the diaphgram parallel to and facing the boundary.^[17] While the patent has expired, "Pressure Zone Microphone" and "PZM" are still active trademarks of Crown International, and the generic term "boundary microphone" is preferred. While a boundary microphone was initially implemented using an omnidirectional element, it is also possible to mount a directional microphone close enough to the surface to gain some of the benefits of this technique while retaining the directional properties of the element. Crown's trademark on this approach is "Phase Coherent Cardioid" or "PCC," but there are other makers who employ this technique as well.

Application-specific designs[link]

A lavalier microphone is made for hands-free operation. These small microphones are worn on the body. Originally, they were held in place with a lanyard worn around the neck, but more often they are fastened to clothing with a clip, pin, tape or magnet. The lavalier cord may be hidden by clothes and either run to an RF transmitter in a pocket or clipped to a belt (for mobile use), or run directly to the mixer (for stationary applications).

A wireless microphone transmits the audio as a radio or optical signal rather than via a cable. It usually sends its signal using a small FM radio transmitter to a nearby receiver connected to the sound system, but it can also use infrared waves if the transmitter and receiver are within sight of each other.

A contact microphone picks up vibrations directly from a solid surface or object, as opposed to sound vibrations carried through air. One use for this is to detect sounds of a very low level, such as those from small objects or insects. The microphone commonly consists of a magnetic (moving coil) transducer, contact plate and contact pin. The contact plate is placed directly on the vibrating part of a musical instrument or other surface, and the contact pin transfers vibrations to the coil. Contact microphones have been used to pick up the sound of a snail's heartbeat and the footsteps of ants. A portable version of this microphone has recently been developed. A throat microphone is a variant of the contact microphone that picks up speech directly from a person's throat, which it is strapped to. This lets the device be used in areas with ambient sounds that would otherwise make the speaker inaudible.

A parabolic microphone uses a parabolic reflector to collect and focus sound waves onto a microphone receiver, in much the same way that a parabolic antenna (e.g. satellite dish) does with radio waves. Typical uses of this microphone, which has unusually focused front sensitivity and can pick up sounds from many meters away, include nature recording, outdoor sporting events, eavesdropping, law enforcement, and even espionage. Parabolic microphones are not typically used for standard recording applications, because they tend to have poor low-frequency response as a side effect of their design.

A stereo microphone integrates two microphones in one unit to produce a stereophonic signal. A stereo microphone is often used for broadcast applications or field recording where it would be impractical to configure two separate condenser microphones in a classic X-Y configuration (see microphone practice) for stereophonic recording. Some such microphones have an adjustable angle of coverage between the two channels.

A noise-canceling microphone is a highly directional design intended for noisy environments. One such use is in aircraft cockpits where they are normally installed as boom microphones on headsets. Another use is in live event support on loud concert stages for vocalists involved with live performances. Many noise-canceling microphones combine signals received from two diaphragms that are in opposite electrical polarity or are processed electronically. In dual diaphragm designs, the main diaphragm is mounted closest to the intended source and the second is positioned farther away from the source so that it can pick up environmental sounds to be subtracted from the main diaphragm's signal. After the two signals have been combined, sounds other than the intended source are greatly reduced, substantially increasing intelligibility. Other noise-canceling designs use one diaphragm that is affected by ports open to the sides and rear of the microphone, with the sum being a 16 dB rejection of sounds that are farther away. One noise-canceling headset design using a single diaphragm has been used prominently by vocal artists such as Garth Brooks and Janet Jackson.^[18] A few noise-canceling microphones are throat microphones.

Connectors[link]

Electronic symbol for a microphone

The most common connectors used by microphones are:

• Male XLR connector on professional microphones
• ¼ inch (sometimes referred to as 6.3 mm) jack plug also known as 1/4 inch TRS connector on less expensive consumer microphones. Many consumer microphones use an unbalanced 1/4 inch phone jack. Harmonica microphones commonly use a high impedance 1/4 inch TS connection to be run through guitar amplifiers.
• 3.5 mm (sometimes referred to as 1/8 inch mini) stereo (wired as mono) mini phone plug on very inexpensive and computer microphones

A microphone with a USB connector, made by Blue Microphones

Some microphones use other connectors, such as a 5-pin XLR, or mini XLR for connection to portable equipment. Some lavalier (or 'lapel', from the days of attaching the microphone to the news reporters suit lapel) microphones use a proprietary connector for connection to a wireless transmitter. Since 2005, professional-quality microphones with USB connections have begun to appear, designed for direct recording into computer-based software.

Impedance-matching[link]

Microphones have an electrical characteristic called impedance, measured in ohms (Ω), that depends on the design. Typically, the rated impedance is stated.^[19] Low impedance is considered under 600 Ω. Medium impedance is considered between 600 Ω and 10 kΩ. High impedance is above 10 kΩ. Owing to their built-in amplifier, condenser microphones typically have an output impedance between 50 and 200 Ω.^[20]

The output of a given microphone delivers the same power whether it is low or high impedance. If a microphone is made in high and low impedance versions, the high impedance version has a higher output voltage for a given sound pressure input, and is suitable for use with vacuum-tube guitar amplifiers, for instance, which have a high input impedance and require a relatively high signal input voltage to overcome the tubes' inherent noise. Most professional microphones are low impedance, about 200 Ω or lower. Professional vacuum-tube sound equipment incorporates a transformer that steps up the impedance of the microphone circuit to the high impedance and voltage needed to drive the input tube; the impedance conversion inherently creates voltage gain as well. External matching transformers are also available that can be used in-line between a low impedance microphone and a high impedance input.

Low-impedance microphones are preferred over high impedance for two reasons: one is that using a high-impedance microphone with a long cable results in high frequency signal loss due to cable capacitance, which forms a low-pass filter with the microphone output impedance. The other is that long high-impedance cables tend to pick up more hum (and possibly radio-frequency interference (RFI) as well). Nothing is damaged if the impedance between microphone and other equipment is mismatched; the worst that happens is a reduction in signal or change in frequency response.

Most microphones are designed not to have their impedance matched by the load they are connected to.^[21] Doing so can alter their frequency response and cause distortion, especially at high sound pressure levels. Certain ribbon and dynamic microphones are exceptions, due to the designers' assumption of a certain load impedance being part of the internal electro-acoustical damping circuit of the microphone.^{[22][dubious – discuss]}

Digital microphone interface[link]

Neumann D-01 digital microphone and Neumann DMI-8 8-channel USB Digital Microphone Interface

The AES 42 standard, published by the Audio Engineering Society, defines a digital interface for microphones. Microphones conforming to this standard directly output a digital audio stream through an XLR or XLD male connector, rather than producing an analog output. Digital microphones may be used either with new equipment with appropriate input connections that conform to the AES 42 standard, or else via a suitable interface box. Studio-quality microphones that operate in accordance with the AES 42 standard are now available from a number of microphone manufacturers.

Measurements and specifications[link]

A comparison of the far field on-axis frequency response of the Oktava 319 and the Shure SM58

Because of differences in their construction, microphones have their own characteristic responses to sound. This difference in response produces non-uniform phase and frequency responses. In addition, microphones are not uniformly sensitive to sound pressure, and can accept differing levels without distorting. Although for scientific applications microphones with a more uniform response are desirable, this is often not the case for music recording, as the non-uniform response of a microphone can produce a desirable coloration of the sound. There is an international standard for microphone specifications,^[19] but few manufacturers adhere to it. As a result, comparison of published data from different manufacturers is difficult because different measurement techniques are used. The Microphone Data Website has collated the technical specifications complete with pictures, response curves and technical data from the microphone manufacturers for every currently listed microphone, and even a few obsolete models, and shows the data for them all in one common format for ease of comparison.[1]. Caution should be used in drawing any solid conclusions from this or any other published data, however, unless it is known that the manufacturer has supplied specifications in accordance with IEC 60268-4.

A frequency response diagram plots the microphone sensitivity in decibels over a range of frequencies (typically 20 Hz to 20 kHz), generally for perfectly on-axis sound (sound arriving at 0° to the capsule). Frequency response may be less informatively stated textually like so: "30 Hz–16 kHz ±3 dB". This is interpreted as meaning a nearly flat, linear, plot between the stated frequencies, with variations in amplitude of no more than plus or minus 3 dB. However, one cannot determine from this information how smooth the variations are, nor in what parts of the spectrum they occur. Note that commonly made statements such as "20 Hz–20 kHz" are meaningless without a decibel measure of tolerance. Directional microphones' frequency response varies greatly with distance from the sound source, and with the geometry of the sound source. IEC 60268-4 specifies that frequency response should be measured in plane progressive wave conditions (very far away from the source) but this is seldom practical. Close talking microphones may be measured with different sound sources and distances, but there is no standard and therefore no way to compare data from different models unless the measurement technique is described.

The self-noise or equivalent noise level is the sound level that creates the same output voltage as the microphone does in the absence of sound. This represents the lowest point of the microphone's dynamic range, and is particularly important should you wish to record sounds that are quiet. The measure is often stated in dB(A), which is the equivalent loudness of the noise on a decibel scale frequency-weighted for how the ear hears, for example: "15 dBA SPL" (SPL means sound pressure level relative to 20 micropascals). The lower the number the better. Some microphone manufacturers state the noise level using ITU-R 468 noise weighting, which more accurately represents the way we hear noise, but gives a figure some 11–14 dB higher. A quiet microphone typically measures 20 dBA SPL or 32 dB SPL 468-weighted. Very quiet microphones have existed for years for special applications, such the Brüel & Kjaer 4179, with a noise level around 0 dB SPL. Recently some microphones with low noise specifications have been introduced in the studio/entertainment market, such as models from Neumann and Røde that advertise noise levels between 5–7 dBA. Typically this is achieved by altering the frequency response of the capsule and electronics to result in lower noise within the A-weighting curve while broadband noise may be increased.

The maximum SPL the microphone can accept is measured for particular values of total harmonic distortion (THD), typically 0.5%. This amount of distortion is generally inaudible^{[citation needed]}, so one can safely use the microphone at this SPL without harming the recording. Example: "142 dB SPL peak (at 0.5% THD)". The higher the value, the better, although microphones with a very high maximum SPL also have a higher self-noise.

The clipping level is an important indicator of maximum usable level, as the 1% THD figure usually quoted under max SPL is really a very mild level of distortion, quite inaudible especially on brief high peaks. Clipping is much more audible. For some microphones the clipping level may be much higher than the max SPL.

The dynamic range of a microphone is the difference in SPL between the noise floor and the maximum SPL. If stated on its own, for example "120 dB", it conveys significantly less information than having the self-noise and maximum SPL figures individually.

Sensitivity indicates how well the microphone converts acoustic pressure to output voltage. A high sensitivity microphone creates more voltage and so needs less amplification at the mixer or recording device. This is a practical concern but is not directly an indication of the microphone's quality, and in fact the term sensitivity is something of a misnomer, "transduction gain" being perhaps more meaningful, (or just "output level") because true sensitivity is generally set by the noise floor, and too much "sensitivity" in terms of output level compromises the clipping level. There are two common measures. The (preferred) international standard is made in millivolts per pascal at 1 kHz. A higher value indicates greater sensitivity. The older American method is referred to a 1 V/Pa standard and measured in plain decibels, resulting in a negative value. Again, a higher value indicates greater sensitivity, so −60  dB is more sensitive than −70 dB.

Measurement microphones[link]

Some microphones are intended for testing speakers, measuring noise levels and otherwise quantifying an acoustic experience. These are calibrated transducers and are usually supplied with a calibration certificate that states absolute sensitivity against frequency. The quality of measurement microphones is often referred to using the designations "Class 1," "Type 2" etc., which are references not to microphone specifications but to sound level meters.^[23] A more comprehensive standard^[24] for the description of measurement microphone performance was recently adopted.

Measurement microphones are generally scalar sensors of pressure; they exhibit an omnidirectional response, limited only by the scattering profile of their physical dimensions. Sound intensity or sound power measurements require pressure-gradient measurements, which are typically made using arrays of at least two microphones, or with hot-wire anemometers.

Microphone calibration[link]

To take a scientific measurement with a microphone, its precise sensitivity must be known (in volts per pascal). Since this may change over the lifetime of the device, it is necessary to regularly calibrate measurement microphones. This service is offered by some microphone manufacturers and by independent certified testing labs. All microphone calibration is ultimately traceable to primary standards at a national measurement institute such as NPL in the UK, PTB in Germany and NIST in the United States, which most commonly calibrate using the reciprocity primary standard. Measurement microphones calibrated using this method can then be used to calibrate other microphones using comparison calibration techniques.

Depending on the application, measurement microphones must be tested periodically (every year or several months, typically) and after any potentially damaging event, such as being dropped (most such microphones come in foam-padded cases to reduce this risk) or exposed to sounds beyond the acceptable level.

Microphone array and array microphones[link]

A microphone array is any number of microphones operating in tandem. There are many applications:

• Systems for extracting voice input from ambient noise (notably telephones, speech recognition systems, hearing aids)
• Surround sound and related technologies
• Locating objects by sound: acoustic source localization, e.g., military use to locate the source(s) of artillery fire. Aircraft location and tracking.
• High fidelity original recordings
• 3D spatial beamforming for localized acoustic detection of subcutaneous sounds

Typically, an array is made up of omnidirectional microphones distributed about the perimeter of a space, linked to a computer that records and interprets the results into a coherent form.

Microphone windscreens[link]

Various microphone covers

Windscreens^{[note 1]} are used to protect microphones that would otherwise be buffeted by wind or vocal plosives from consonants such as "P", "B", etc. Most microphones have an integral windscreen built around the microphone diaphragm. A screen of plastic, wire mesh or a metal cage is held at a distance from the microphone diaphragm, to shield it. This cage provides a first line of defense against the mechanical impact of objects or wind. Some microphones, such as the Shure SM58, may have an additional layer of foam inside the cage to further enhance the protective properties of the shield. One disadvantage of all windscreen types is that the microphone's high frequency response is attenuated by a small amount, depending on the density of the protective layer.

Beyond integral microphone windscreens, there are three broad classes of additional wind protection.

Microphone covers[link]

Microphone covers are often made of soft open-cell polyester or polyurethane foam because of the inexpensive, disposable nature of the foam. Optional windscreens are often available from the manufacturer and third parties. A visible example of an optional accessory windscreen is the A2WS from Shure, one of which is fitted over each of the two Shure SM57 microphones used on the United States president's lectern.^[25] One disadvantage of polyurethane foam microphone covers is that they can deteriorate over time. Windscreens also tend to collect dirt and moisture in their open cells and must be cleaned to prevent high frequency loss, bad odor and unhealthy conditions for the person using the microphone. On the other hand, a major advantage of concert vocalist windscreens is that one can quickly change to a clean windscreen between users, reducing the chance of transferring germs. Windscreens of various colors can be used to distinguish one microphone from another on a busy, active stage.

Pop filter by Gauge Precision Instruments

Pop filters[link]

Pop filters or pop screens are used in controlled studio environments to minimize plosives when recording. A typical pop filter is composed of one or more layers of acoustically transparent gauze-like material, such as woven nylon (e.g., pantyhose) stretched over a circular frame and a clamp and a flexible mounting bracket to attach to the microphone stand. The pop shield is placed between the vocalist and the microphone. The closer a vocalist brings his or her lips to the microphone, the greater the requirement for a pop filter. Singers can be trained either to soften their plosives or direct the air blast away from the microphone, in which cases they don't need a pop filter.

Pop filters also keep spittle off the microphone. Most condenser microphones can be damaged by spittle.

Blimps[link]

Two recordings being made — a blimp is being used on the left. An open-cell foam windscreen is being used on the right.

"Dead cat" and a "dead kitten" windscreens. The dead kitten covers a stereo microphone for a DSLR camera. The difference in name is due to the size of the fur.

Blimps (also known as Zeppelins) are large, hollow windscreens used to surround microphones for outdoor location audio, such as nature recording, electronic news gathering, and for film and video shoots. They can cut wind noise by as much as 25 dB, especially low-frequency noise. The blimp is essentially a hollow cage or basket with acoustically transparent material stretched over the outer frame. The blimp works by creating a volume of still air around the microphone. The microphone is often further isolated from the blimp by an elastic suspension inside the basket. This reduces wind vibrations and handling noise transmitted from the cage. To extend the range of wind speed conditions in which the blimp remains effective, many have the option of a secondary cover over the outer shell. This is usually an acoustically transparent, synthetic fur material with long, soft hairs. Common and slang names for this include "dead cat" or "windmuff". The hairs deaden the noise caused by the shock of wind hitting the blimp. A synthetic fur cover can reduce wind noise by an additional 10 dB.^[26]

See also[link]

Electronics portal

• Hydrophone (microphone for underwater use)
• Geophone (microphone for use within the earth)
• Ionophone (plasma-based microphone)
• Microphone connector
• Nominal impedance
• Shock mount - Microphone mount that suspends the microphone in elastic straps

Notes[link]

1. ^ A microphone windscreen is sometimes called a wind gag, or dead cat or yeti.

References[link]

External links[link]

Wikimedia Commons has media related to: Microphones

• Info, Pictures and Soundbytes from vintage microphones
• Microphone sensitivity conversion – dB re 1 V/Pa and transfer factor mV/Pa
• Searchable database of specs and component info from 1000+ microphones
• Microphone construction and basic placement advice
• History of the Microphone
• Large vs. Small Diaphragms in Omnidirectional Microphones
• Guide to Condenser Microphones
• Measurement/Engineering Grade Microphone Basics

Ronald Reagan
40th President of the United States
In office January 20, 1981 – January 20, 1989
Vice President	George H. W. Bush
Preceded by	Jimmy Carter
Succeeded by	George H. W. Bush
33rd Governor of California
In office January 2, 1967 – January 6, 1975
Lieutenant	Robert Finch Edwin Reinecke John Harmer
Preceded by	Pat Brown
Succeeded by	Jerry Brown
Personal details
Born	Ronald Wilson Reagan (1911-02-06)February 6, 1911 Tampico, Illinois, U.S.
Died	June 5, 2004(2004-06-05) (aged 93) Los Angeles, California, U.S.
Resting place	Ronald Reagan Presidential Library, Simi Valley, California, U.S. 34°15′35.5896″N 118°49′11.301″W / 34.259886°N 118.81980583°W / 34.259886; -118.81980583
Political party	Republican (1962–2004)
Other political affiliations	Democratic (Before 1962)
Spouse(s)	Jane Wyman (1940–1949) Nancy Davis (1952–2004)
Children	Maureen Christine Michael Patti Ron
Alma mater	Eureka College
Religion	Disciples of Christ later Presbyterian
Signature
Military service
Service/branch	United States Army United States Army Air Forces
Years of service	1937–45
Rank	Captain

Ronald Wilson Reagan ( /ˈrɒnəld ˈwɪlsən ˈreɪɡən/; February 6, 1911 – June 5, 2004) was the 40th President of the United States, serving from 1981 to 1989. Prior to that, he was the 33rd Governor of California from 1967 to 1975 and a radio, film and television actor.

Born in Tampico, Illinois and raised in Dixon, Reagan was educated at Eureka College, earning a Bachelor of Arts degree in economics and sociology. After his graduation, Reagan moved first to Iowa to work as a radio broadcaster and then in to Los Angeles in 1937 where he began a career as an actor, first in films and later television. Some of his most notable films include Knute Rockne, All American, Kings Row, and Bedtime for Bonzo. Reagan served as president of the Screen Actors Guild, and later as a spokesman for General Electric (GE); his start in politics occurred during his work for GE. Originally a member of the Democratic Party, his positions began shifting rightward in the late 1950s, and he switched to the Republican Party in 1962. After delivering a rousing speech in support of Barry Goldwater's presidential candidacy in 1964, he was persuaded to seek the California governorship, winning two years later and again in 1970. He was defeated in his run for the Republican presidential nomination in 1968 as well as 1976, but won both the nomination and general election in 1980, defeating incumbent Jimmy Carter.

As president, Reagan implemented sweeping new political and economic initiatives. His supply-side economic policies, dubbed "Reaganomics", advocated reducing tax rates to spur economic growth, controlling the money supply to reduce inflation, deregulation of the economy, and reducing government spending. In his first term he survived an assassination attempt, took a hard line against labor unions, and ordered an invasion of Grenada. He was reelected in a landslide in 1984, proclaiming that it was "Morning in America." His second term was primarily marked by foreign matters, such as the ending of the Cold War, the 1986 bombing of Libya, and the revelation of the Iran-Contra affair. Publicly describing the Soviet Union as an "evil empire,"^[1] he supported anti-communist movements worldwide and spent his first term forgoing the strategy of détente by ordering a massive military buildup in an arms race with the USSR. Reagan negotiated with Soviet General Secretary Mikhail Gorbachev, culminating in the INF Treaty and the decrease of both countries' nuclear arsenals.

Reagan left office in 1989. In 1994, the former president disclosed that he had been diagnosed with Alzheimer's disease earlier in the year; he died ten years later at the age of 93. He ranks highly in public opinion polls of U.S. Presidents and is credited for generating an ideological renaissance on the American political right.

Early life[link]

Ronald Reagan as a teenager in Dixon, Illinois

Ronald Wilson Reagan was born in an apartment on the second floor of a commercial building in Tampico, Illinois on February 6, 1911, to Jack Reagan and Nelle Wilson Reagan.^[2] Reagan's father was a salesman and a storyteller, the grandson of Irish Catholic immigrants from County Tipperary^[3] while his mother had Scots and English ancestors.^[4] Reagan had one sibling, his older brother, Neil (1908–1996), who became an advertising executive.^[5] As a boy, Reagan's father nicknamed his son "Dutch", due to his "fat little Dutchman"-like appearance, and his "Dutchboy" haircut;^[6] the nickname stuck with him throughout his youth.^[6] Reagan's family briefly lived in several towns and cities in Illinois, including Monmouth, Galesburg and Chicago, until 1919, when they returned to Tampico and lived above the H.C. Pitney Variety Store.^[2] After his election as president, residing in the upstairs White House private quarters, Reagan would quip that he was "living above the store again".^[7]

According to Paul Kengor, author of God and Ronald Reagan, Reagan had a particularly strong faith in the goodness of people, which stemmed from the optimistic faith of his mother, Nelle,^[8] and the Disciples of Christ faith,^[8] which he was baptized into in 1922.^[9] For the time, Reagan was unusual in his opposition to racial discrimination, and recalled a time in Dixon when the local inn would not allow black people to stay there. Reagan brought them back to his house, where his mother invited them to stay the night and have breakfast the next morning.^[10]

Following the closure of the Pitney Store in late 1920, the Reagans moved to Dixon;^[11] the midwestern "small universe" had a lasting impression on Reagan.^[12] He attended Dixon High School,^[13] where he developed interests in acting, sports, and storytelling.^[14] His first job was as a lifeguard at the Rock River in Lowell Park, near Dixon, in 1927. Reagan performed 77 rescues as a lifeguard, noting that he notched a mark on a wooden log for every life he saved.^[14] Reagan attended Eureka College, where he became a member of the Tau Kappa Epsilon fraternity, a cheerleader,^[15] and majored in economics and sociology. He developed a reputation as a jack of all trades, excelling in campus politics, sports and theater. He was a member of the football team, captain of the swim team and was elected student body president. As student president, Reagan led a student revolt against the college president after he tried to cut back the faculty.^[16]

Entertainment career[link]

Radio and film[link]

Trailer from Love is on the Air starring Reagan, 1937

After graduating from Eureka in 1932, Reagan drove himself to Iowa, where he auditioned for a job at many small-town radio stations.^[17] The University of Iowa hired him to broadcast home football games for the Hawkeyes. He was paid $10 per game.^[17] Soon after, a staff announcer's job opened at radio station WOC in Davenport, and Reagan was hired, now earning $100 per month.^[17] Aided by his persuasive voice,^[17] he moved to WHO radio in Des Moines as an announcer for Chicago Cubs baseball games.^[18] His specialty was creating play-by-play accounts of games that the station received by wire.^[17]

While traveling with the Cubs in California, Reagan took a screen test in 1937 that led to a seven-year contract with Warner Brothers studios.^[19] He spent the first few years of his Hollywood career in the "B film" unit, where, Reagan joked, the producers "didn't want them good, they wanted them Thursday".^[17] While sometimes overshadowed by other actors, Reagan's screen performances did receive many good reviews.^[17]

Reagan in Kings Row, which gave a brief boost to his career, in 1942. Trailer from the film.

His first screen credit was the starring role in the 1937 movie Love Is on the Air, and by the end of 1939 he had already appeared in 19 films,^[20] including Dark Victory. Before the film Santa Fe Trail in 1940, he played the role of George "The Gipper" Gipp in the film Knute Rockne, All American; from it, he acquired the lifelong nickname "the Gipper".^[21] In 1941 exhibitors voted him the fifth most popular star from the younger generation in Hollywood.^[22]

Reagan's favorite acting role was as a double amputee in 1942's Kings Row,^[23] in which he recites the line, "Where's the rest of me?", later used as the title of his 1965 autobiography. Many film critics considered Kings Row to be his best movie,^[24] though the film was condemned by New York Times critic Bosley Crowther.^[25][26]

Although, Reagan called Kings Row the film that "made me a star",^[27] he was unable to capitalize on his success because he was ordered to active duty with the U.S. Army at San Francisco two months after its release, and never regained "star" status in motion pictures.^[27] In the post-war era, after being separated from almost four years of World War II stateside service with the 1st Motion Picture Unit in December 1945, Reagan co-starred in such films as, The Voice of the Turtle, John Loves Mary, The Hasty Heart, Bedtime for Bonzo, Cattle Queen of Montana, Tennessee's Partner, Hellcats of the Navy and The Killers (his final film) in a 1964 remake.^[28] Throughout his film career, his mother often answered much of his fan mail.^[29]

Military service[link]

After completing fourteen home-study Army Extension Courses, Reagan enlisted in the Army Enlisted Reserve^[30] on April 29, 1937, as a private assigned to Troop B, 322nd Cavalry at Des Moines, Iowa.^[31] He was commissioned a Second Lieutenant in the Officers Reserve Corps of the Cavalry on May 25, 1937.^[32]

Reagan was ordered to active duty for the first time on April 18, 1942. Due to his nearsightedness, he was classified for limited service only, which excluded him from serving overseas.^[33] His first assignment was at the San Francisco Port of Embarkation at Fort Mason, California, as a liaison officer of the Port and Transportation Office.^[34] Upon the approval of the Army Air Force (AAF), he applied for a transfer from the Cavalry to the AAF on May 15, 1942, and was assigned to AAF Public Relations and subsequently to the First Motion Picture Unit (officially, the "18th AAF Base Unit") in Culver City, California.^[34] On January 14, 1943 he was promoted to First Lieutenant and was sent to the Provisional Task Force Show Unit of This Is The Army at Burbank, California.^[34] He returned to the First Motion Picture Unit after completing this duty and was promoted to Captain on July 22, 1943.^[31]

In January 1944, Captain Reagan was ordered to temporary duty in New York City to participate in the opening of the sixth War Loan Drive. He was re-assigned to the First Motion Picture Unit on November 14, 1944, where he remained until the end of World War II.^[31] He was recommended for promotion to Major on February 2, 1945, but this recommendation was disapproved on July 17 of that year.^[35] He returned to Fort MacArthur, California, where he was separated from active duty on December 9, 1945.^[35] By the end of the war, his units had produced some 400 training films for the AAF.^[31]

Reagan never left the United States during the war, though he kept a film reel, obtained while in the service, depicting the liberation of Auschwitz, as he believed that someday doubts would arise as to whether the Holocaust had occurred.^[36] It has been alleged that he was overheard telling Israeli foreign minister Yitzhak Shamir in 1983 that he had filmed that footage himself and helped liberate Auschwitz,^[36][37] though this purported conversation was disputed by Secretary of State George Shultz.^[38]

SAG president and television[link]

Television star Ronald Reagan as the host of General Electric Theater

Reagan was first elected to the Board of Directors of the Screen Actors Guild in 1941, serving as an alternate. Following World War II, he resumed service and became 3rd vice-president in 1946.^[39] The adoption of conflict-of-interest bylaws in 1947 led the SAG president and six board members to resign; Reagan was nominated in a special election for the position of president and subsequently elected.^[39] He was subsequently chosen by the membership to serve seven additional one-year terms, from 1947 to 1952 and in 1959.^[39] Reagan led SAG through eventful years that were marked by labor-management disputes, the Taft-Hartley Act, House Committee on Un-American Activities (HUAC) hearings and the Hollywood blacklist era.^[39]

Amid the Red Scare in the late 1940s, Reagan provided the FBI with names of actors whom he believed to be communist sympathizers within the motion picture industry.^[40] Reagan testified before the House Un-American Activities Committee on the subject as well.^[41] A fervent anti-communist, he reaffirmed his commitment to democratic principles, stating, "I never as a citizen want to see our country become urged, by either fear or resentment of this group, that we ever compromise with any of our democratic principles through that fear or resentment."^[41]

Though an early critic of television, Reagan landed fewer film roles in the late 1950s and decided to join the medium.^[17] He was hired as the host of General Electric Theater, a series of weekly dramas that became very popular.^[17] His contract required him to tour GE plants sixteen weeks out of the year, often demanding of him fourteen speeches per day.^[17] He earned approximately $125,000 per year (about $1.07 million in 2010 dollars) in this role. His final work as a professional actor was as host and performer from 1964 to 1965 on the television series Death Valley Days.^{[28][better source needed]} Reagan and Nancy Davis appeared together several times, including an episode of GE Theater in 1958 called A Turkey for the President.^{[42][better source needed]}

Marriages and children[link]

In 1938, Reagan co-starred in the film Brother Rat with actress Jane Wyman (1917–2007). They were engaged at the Chicago Theatre,^[43] and married on January 26, 1940, at the Wee Kirk o' the Heather church in Glendale, California.^[44] Together they had two biological children, Maureen (1941–2001) and Christine (who was born in 1947 but only lived one day), and adopted a third, Michael (born 1945).^[45] Following arguments about Reagan's political ambitions, Wyman filed for divorce in 1948,^[46] citing a distraction due to her husband's Screen Actors Guild union duties; the divorce was finalized in 1949.^[21] He is the only US president to have been divorced.^[47]

Ronald and Nancy Reagan aboard a boat in California in 1964

Reagan met actress Nancy Davis (born 1921)^[48] in 1949 after she contacted him in his capacity as president of the Screen Actors Guild to help her with issues regarding her name appearing on a communist blacklist in Hollywood (she had been mistaken for another Nancy Davis). She described their meeting by saying, "I don't know if it was exactly love at first sight, but it was pretty close."^[49] They were engaged at Chasen's restaurant in Los Angeles and were married on March 4, 1952, at the Little Brown Church in the San Fernando Valley.^[50] Actor William Holden served as best man at the ceremony. They had two children: Patti (born October 21, 1952) and Ron (born May 20, 1958).

Observers described the Reagans' relationship as close, authentic and intimate.^[51] During his presidency they were reported to frequently display their affection for one another; one press secretary said, "They never took each other for granted. They never stopped courting."^[49][52] He often called her "Mommy" she called him "Ronnie".^[52] He once wrote to her, "Whatever I treasure and enjoy ... all would be without meaning if I didn't have you."^[53] When he was in the hospital in 1981, she slept with one of his shirts to be comforted by his scent.^[54] In a letter to U.S. citizens written in 1994, Reagan wrote "I have recently been told that I am one of the millions of Americans who will be afflicted with Alzheimer's disease.... I only wish there was some way I could spare Nancy from this painful experience,"^[49] and in 1998, while Reagan was stricken by Alzheimer's, Nancy told Vanity Fair, "Our relationship is very special. We were very much in love and still are. When I say my life began with Ronnie, well, it's true. It did. I can't imagine life without him."^[49]

Early political career[link]

Reagan began his political career as a liberal Democrat, admirer of Franklin D. Roosevelt, and an active supporter of New Deal policies. In the early 1950s, as his relationship with Republican actress Nancy Davis grew,^[55][56] he shifted to the right and, while remaining a Democrat, endorsed the presidential candidacies of Dwight D. Eisenhower in 1952 and 1956 as well as Richard Nixon in 1960.^[57] The last time Reagan actively supported a Democratic candidate was in 1950 when he helped Helen Gahagan Douglas in her unsuccessful Senate campaign against Richard Nixon.^[58] After being hired in 1954 to host the General Electric Theater, a TV drama series,^[59] Reagan soon began to embrace the conservative views of the sponsoring company's officials.^[59][60] His many GE speeches—which he wrote himself—were non-partisan but carried a conservative, pro-business message; he was influenced by Lemuel Boulware, a senior GE executive. Boulware, known for his tough stance against unions and his innovative strategies to win over workers, championed the core tenets of modern American conservatism: free markets, anticommunism, lower taxes, and limited government.^[61] Eventually, the ratings for Reagan's show fell off and GE dropped Reagan in 1962.^[62] In August of that year Reagan formally switched to the Republican Party, stating, "I didn't leave the Democratic Party. The party left me."^[63]

In the early 1960s Reagan opposed certain civil rights legislation, saying that "if an individual wants to discriminate against Negroes or others in selling or renting his house, it is his right to do so."^[64] In his rationale, he cited his opposition to government intrusion into personal freedoms, as opposed to racism; he strongly denied having racist motives and later reversed his opposition to voting rights and fair housing laws.^[65] When legislation that would become Medicare was introduced in 1961, Reagan created a recording for the American Medical Association warning that such legislation would mean the end of freedom in America. Reagan said that if his listeners did not write letters to prevent it, "we will awake to find that we have so­cialism. And if you don't do this, and if I don't do it, one of these days, you and I are going to spend our sunset years telling our children, and our children's children, what it once was like in America when men were free."^[66][67][68] He also joined the National Rifle Association and would become a lifetime member.^[69]

Reagan endorsed the campaign of conservative presidential contender Barry Goldwater in 1964. Speaking for Goldwater, Reagan stressed his belief in the importance of smaller government. He revealed his ideological motivation in a famed speech delivered on October 27, 1964: "The Founding Fathers knew a government can't control the economy without controlling people. And they knew when a government sets out to do that, it must use force and coercion to achieve its purpose. So we have come to a time for choosing."^[70] He also said, "You and I are told we must choose between a left or right, but I suggest there is no such thing as a left or right. There is only an up or down. Up to man's age-old dream – the maximum of individual freedom consistent with order – or down to the ant heap of totalitarianism."^[70][71] This "A Time for Choosing" speech raised $1 million for Goldwater's campaign^[17] and is considered the event that launched Reagan's political career.^[72]

Governor of California, 1967–1975[link]

Ronald and Nancy Reagan celebrate Reagan's gubernatorial victory at the Biltmore Hotel in Los Angeles.

California Republicans were impressed with Reagan's political views and charisma after his "Time for Choosing" speech,^[73] and nominated him for Governor of California in 1966. In Reagan's campaign, he emphasized two main themes: "to send the welfare bums back to work", and, in reference to burgeoning anti-war and anti-establishment student protests at the University of California at Berkeley, "to clean up the mess at Berkeley".^[74] He was elected, defeating two-term governor Edmund G. "Pat" Brown, and was sworn in on January 2, 1967. In his first term, he froze government hiring and approved tax hikes to balance the budget.^[75]

Shortly after the beginning of his term, Reagan tested the presidential waters in 1968 as part of a "Stop Nixon" movement, hoping to cut into Nixon's Southern support^[76] and be a compromise candidate^[77] if neither Nixon nor second-place Nelson Rockefeller received enough delegates to win on the first ballot at the Republican convention. However, by the time of the convention Nixon had 692 delegate votes, 25 more than he needed to secure the nomination, followed by Rockefeller with Reagan in third place.^[76]

Reagan was involved in high-profile conflicts with the protest movements of the era. On May 15, 1969, during the People's Park protests at UC Berkeley, Reagan sent the California Highway Patrol and other officers to quell the protests, in an incident that became known as "Bloody Thursday", resulting in the death of student James Rector and the blinding of carpenter Alan Blanchard.^[78][79] Reagan then called out 2,200 state National Guard troops to occupy the city of Berkeley for two weeks in order to crack down on the protesters.^[78] A year after "Bloody Thursday", Reagan responded to questions about campus protest movements saying, "If it takes a bloodbath, let's get it over with. No more appeasement."^[80] When the Symbionese Liberation Army kidnapped Patty Hearst in Berkeley and demanded the distribution of food to the poor, Reagan joked, "It's just too bad we can't have an epidemic of botulism."^[81]

The Reagans meeting with then-President Richard Nixon and First Lady Pat Nixon in July 1970

Early in 1967, the national debate on abortion was beginning. Democratic California state senator Anthony Beilenson introduced the "Therapeutic Abortion Act," in an effort to reduce the number of "back-room abortions" performed in California.^[78] The State Legislature sent the bill to Reagan's desk where, after many days of indecision, he signed it.^[82] About two million abortions would be performed as a result, most because of a provision in the bill allowing abortions for the well-being of the mother.^[82] Reagan had been in office for only four months when he signed the bill, and stated that had he been more experienced as governor, it would not have been signed. After he recognized what he called the "consequences" of the bill, he announced that he was pro-life.^[82] He maintained that position later in his political career, writing extensively about abortion.^[83]

Despite an unsuccessful attempt to recall him in 1968,^[84] Reagan was re-elected in 1970, defeating "Big Daddy" Jesse Unruh. He chose not to seek a third term in the following election cycle. One of Reagan's greatest frustrations in office concerned capital punishment, which he strongly supported.^[23] His efforts to enforce the state's laws in this area were thwarted when the Supreme Court of California issued its People v. Anderson decision, which invalidated all death sentences issued in California prior to 1972, though the decision was later overturned by a constitutional amendment. The only execution during Reagan's governorship was on April 12, 1967, when Aaron Mitchell's sentence was carried out by the state in San Quentin's gas chamber.^[85]

In 1969, Reagan, as Governor, signed the Family Law Act which was the first no fault divorce legislation in the United States.^[86]

Reagan's terms as governor helped to shape the policies he would pursue in his later political career as president. By campaigning on a platform of sending "the welfare bums back to work", he spoke out against the idea of the welfare state. He also strongly advocated the Republican ideal of less government regulation of the economy, including that of undue federal taxation.^[87]

Reagan did not seek re-election to a third term as governor in 1974 and was succeeded by Democratic California Secretary of State Jerry Brown on January 6, 1975.

1976 presidential campaign[link]

Ronald Reagan on the podium with Gerald Ford at the 1976 Republican National Convention after narrowly losing the presidential nomination.

In 1976, Reagan challenged incumbent President Gerald Ford in a bid to become the Republican Party's candidate for president. Reagan soon established himself as the conservative candidate with the support of like-minded organizations such as the American Conservative Union which became key components of his political base, while President Ford was considered a more moderate Republican.^[88]

Reagan's campaign relied on a strategy crafted by campaign manager John Sears of winning a few primaries early to damage the inevitability of Ford's likely nomination. Reagan won North Carolina, Texas, and California, but the strategy failed, as^[89] he ended up losing New Hampshire, Florida, and his native Illinois.^[90] The Texas campaign lent renewed hope to Reagan, when he swept all ninety-six delegates chosen in the May 1 primary, with four more awaiting at the state convention. Much of the credit for that victory came from the work of three co-chairmen, including Ernest Angelo, the mayor of Midland, and Ray Barnhart of Houston, whom President Reagan tapped in 1981 as director of the Federal Highway Administration.^[91]

However, as the GOP convention neared, Ford appeared close to victory. Acknowledging his party's moderate wing, Reagan chose moderate Senator Richard Schweiker of Pennsylvania as his running mate if nominated. Nonetheless, Ford prevailed with 1,187 delegates to Reagan's 1,070.^[90] Ford would go on to lose the 1976 Presidential election to the Democrat Jimmy Carter.

Reagan's concession speech emphasized the dangers of nuclear war and the threat posed by the Soviet Union. Though he lost the nomination, he received 307 write-in votes in New Hampshire, 388 votes as an Independent on Wyoming's ballot, and a single electoral vote from a faithless elector in the November election from the state of Washington,^[92] which Ford had won over Democratic challenger Jimmy Carter.

1980 presidential campaign[link]

Reagan campaigns with Nancy and Senator Strom Thurmond (right) in South Carolina, 1980

The 1980 presidential campaign between Reagan and incumbent President Jimmy Carter was conducted during domestic concerns and the ongoing Iran hostage crisis. His campaign stressed some of his fundamental principles: lower taxes to stimulate the economy,^[93] less government interference in people's lives,^[94] states' rights,^[95] a strong national defense,^[94] and restoring the U.S. Dollar to a gold standard.^[96][97]