A noise-canceling microphone is a
microphone
A microphone, colloquially called a mic (), or mike, is a transducer that converts sound into an electrical signal. Microphones are used in many applications such as telephones, hearing aids, public address systems for concert halls and publi ...
that is designed to filter
ambient noise.
Technical details
The development is a special case of the differential microphone topology most commonly used to achieve directionality. All such microphones have at least two ports through which sound enters; a front port normally oriented toward the desired sound and another port that's more distant. The microphone's diaphragm is placed between the two ports; sound arriving from an ambient sound field reaches both ports more or less equally. Sound that's much closer to the front port than to the rear will make more of a pressure gradient between the front and back of the diaphragm, causing it to move more. The microphone's
proximity effect is adjusted so that flat frequency response is achieved for sound sources very close to the front of the mic – typically 1 to 3 cm. Sounds arriving from other angles are subject to steep midrange and bass
rolloff. Commercially and militarily useful noise-canceling microphones have been made since at least 1935 (
Amelia Earhart
Amelia Mary Earhart ( ; July 24, 1897 – January 5, 1939) was an American aviation pioneer. On July 2, 1937, she disappeared over the Pacific Ocean while attempting to become the first female pilot to circumnavigate the world. During her li ...
used one on her 1935 flight from Hawaii to California) and have been made since the 1940s by Roanwell,
Electro-Voice[{{cite web , url=https://martinmitchellsmicrophones.wordpress.com/tag/noise-cancelling-microphone/ , title=Noise-cancelling Microphone , publisher=]WordPress
WordPress (WP, or WordPress.org) is a web content management system. It was originally created as a tool to publish blogs but has evolved to support publishing other web content, including more traditional websites, electronic mailing list, ma ...
, work=Martin Mitchell's Microphones , date=February 16, 2016 , accessdate=May 27, 2020 , archiveurl=https://web.archive.org/web/20200527020304/https://martinmitchellsmicrophones.wordpress.com/tag/noise-cancelling-microphone/ , archivedate=May 27, 2020 , url-status=live and others.
Alternative technologies
Another technique uses two or more microphones and active or passive circuitry to reduce the noise. The primary microphone is closer to the desired source (like a person's mouth). A second mic receives ambient noise. In a noisy environment, both microphones receive noise at a similar level, but the primary mic receives the desired sounds more strongly. Thus if one signal is subtracted from the other (in the simplest sense, by connecting the microphones out of phase) much of the noise is canceled while the desired sound is retained. Other techniques may be used as well, such as using a directional primary mic, to maximize the difference between the two signals and make the cancellation easier to do.
The internal electronic circuitry of an active noise-canceling mic attempts to subtract noise signal from the primary microphone. The circuit may employ passive or active
noise canceling techniques to filter out the noise, producing an output signal that has a lower
noise floor
In signal theory, the noise floor is the measure of the signal created from the sum of all the noise sources and unwanted signals within a measurement system, where noise is defined as any signal other than the one being monitored.
In radio com ...
and a higher
signal-to-noise ratio
Signal-to-noise ratio (SNR or S/N) is a measure used in science and engineering that compares the level of a desired signal to the level of background noise. SNR is defined as the ratio of signal power to noise power, often expressed in deci ...
.
Applications
*
Call center
A call centre (English in the Commonwealth of Nations, Commonwealth spelling) or call center (American English, American spelling; American and British English spelling differences#-re, -er, see spelling differences) is a managed capability th ...
headsets
*
Helicopter
A helicopter is a type of rotorcraft in which Lift (force), lift and thrust are supplied by horizontally spinning Helicopter rotor, rotors. This allows the helicopter to VTOL, take off and land vertically, to hover (helicopter), hover, and ...
pilot headsets
*
Race car
Race, RACE or The Race may refer to:
* Race (biology), an informal taxonomic classification within a species, generally within a sub-species
* Race (human categorization), classification of humans into groups based on physical traits, and/or s ...
driver headsets
* Shipboard communications
* Video Gaming Headsets
See also
*
Noise-cancelling headphones
*
Acoustic quieting
*
Active noise control
Active noise control (ANC), also known as noise cancellation (NC), or active noise reduction (ANR), is a method for reducing unwanted sound by the addition of a second sound specifically designed to cancel the first. The concept was first deve ...
References
U.S. Patent 7,248,708
Microphones
Noise reduction