e/Noise-canceling microphone

Information
has gloss	eng: A noise-canceling microphone is a microphone designed to filter out ambient noise from the desired sound, especially useful in noisy environments. It 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 thats more distant. The microphones diaphragm is placed between the two ports; sound arriving from an ambient sound field reaches both ports more or less equally. Sound thats 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 microphones 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 the 1940's by Roanwell, Electro-Voice and others.
lexicalization	eng: noise-canceling microphone
instance of	(noun) device for converting sound waves into electrical energy mike, microphone