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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 developed in the late 1930s; later developmental work that began in the 1950s eventually resulted in ...
Noise -cancelling headphones alongside a carry case. Noise-cancelling headphones are headphones which suppress unwanted ambient sounds using active noise control. This is distinct from passive headphones which, if they reduce ambient sounds at all, use techniques such as soundproofing . Noise cancellation makes it possible to listen to audio ...
The "QuietComfort 20" (QC20) and QC20i in-ear headphones were released in 2015 and are the company's first in-ear noise cancelling headphones. [19] It received a 2014 Red Dot Design Award. [20] Also, it received a CNET 's Editors' Choice Award of 4.5/5 points for its active noise-cancelling. [21]
Environmental noise regulations usually specify a maximum outdoor noise level of 60 to 65 dB(A), while occupational safety organizations recommend that the maximum exposure to noise is 40 hours per week at 85 to 90 dB(A). For every additional 3 dB(A), the maximum exposure time is reduced by a factor 2, e.g. 20 hours per week at 88 dB(A).
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.
It included a noise cancelling function and was powered either by NiCad batteries (with a battery life of 16 hours on radio pilot and 7.5 hours on cruise control sound) or by power from the aircraft. Series II aviation headsets are distinguished by the dirty windows on the earmuffs or by noting that the off/on switch and down control are ...
Audio signal processing is a subfield of signal processing that is concerned with the electronic manipulation of audio signals. Audio signals are electronic representations of sound waves — longitudinal waves which travel through air, consisting of compressions and rarefactions. The energy contained in audio signals or sound power level is ...
Acoustic quieting. Acoustic quieting is the process of making machinery quieter by damping vibrations to prevent them from reaching an observer. Machinery vibrates, causing sound waves in air, hydroacoustic waves in water, and mechanical stresses in solid matter. Quieting is achieved by absorbing the vibrational energy or minimizing the source ...