Active noise control (ANC) (also known as noise cancellation, or active noise reduction (ANR)) is a method for reducing unwanted sound.

Sound is a P-wave, which consists of a compression phase and a rarefaction phase. A noise-cancellation speaker emits a sound wave with the same amplitude but with inverted phase (also known as antiphase) to the original sound. The waves combine to form a new wave, in a process called interference, and effectively cancel each other out - an effect which is called phase cancellation.

Modern active noise control is generally achieved through the use of analog circuits or Digital Signal Processing. Adaptive algorithms are designed to analyze the waveform of the background aural or nonaural noise, then based on the specific algorithm generates a signal that will either phase shift or invert the polarity of the original signal. This inverted signal (in antiphase) is then amplified and a transducer creates a sound wave directly proportional to the amplitude of the original waveform creating destructive interference. This will effectively reduce the volume of the perceivable noise.

Noise control is an active or passive means of reducing sound emissions, often incentivised by personal comfort, environmental considerations or legal compliance. Practical and efficient noise control is wholly reliant on an accurate diagnosis of what is causing the noise, which first involves finding the source of noise. Once the source of noise has been found, the focus is reducing the noise at source by engineering means.

The most common noise sources can be divided into aerodynamic (fans, pneumatics, combustion, etc) and mechanical (impacts, friction, etc). Effective noise control focuses on reducing the noise from these sources as close to the source as possible. Noise control for aerodynamic sources include quiet air nozzles, pneumatic silencers and quiet fan technology.

In architectural acoustics and environmental acoustics, noise control refers to the set of practices employed for noise mitigation. Within architectural acoustics these practices include: interior sound reverberation reduction, inter-room noise transfer mitigation and exterior building skin augmentation. “More specific architectural noise control methods include the installation of thicker and/ or double-glazed windows,” acoustical gypsum, ceiling tiles, ceiling panels, carpet and draperies. In the field of environmental sound, common noise control practices include: design of noise barriers, development and enforcement of noise abatement legal codes and urban design.

James Daniel May (born 16 January 1963) is an English television presenter, journalist and writer. He is best known for his role as co-presenter of the award-winning motoring program Top Gear alongside Jeremy Clarkson , and Richard Hammond.

On Top Gear, May has the nickname "Captain Slow" for his careful driving style, a love of small underpowered cars and habit of getting lost and distracted while driving. However, in a July 2010 episode of Top Gear he drove a Bugatti Veyron Super Sport, reaching a speed of 417.6 kilometres per hour (259.5 mph). After his attempt the Bugatti test driver Pierre-Henri Raphanel took the car to 430 kilometers per hour (267.5 mph).

May has presented a variety of other programs on themes including science and technology, toys, cars, wine culture, and the plight of manliness in modern times. In addition he has released a variety of DVDs and books with similar themes, and wrote a weekly column for The Daily Telegraph's motoring section.

James May was born in Bristol, one of four children; he has two sisters and a brother. May attended Caerleon Endowed Junior School in Newport, then in Monmouthshire. He spent his teenage years in South Yorkshire where he attended Oakwood Comprehensive School in Rotherham and was a choirboy at Whiston Parish Church. He was also at school with Life On Mars and Ashes to Ashes star Dean Andrews. A keen flautist and pianist, he later studied music at Pendle College, Lancaster University. After graduating, May briefly worked at a hospital in Chelsea as a records officer, and had a short stint in Her Majesty's Civil Service.