Active Noise Reduction
Hearing Protection

What is active noise reduction hearing protection? Does it work? It is worth the cost?

Active noise reduction (ANR), also known as noise cancellation technology, is used in many high-end headphones, to enhance the music sound quality by reducing noise from the external environment. It is also used in some hearing protection devices.

Active noise reduction is circuitry that reads the incoming sound waves, electronically inverts them by phase, and plays the resulting inverted sound waves. Added to the external sound waves in this way, the phases cancel each other out, bringing the amplitude (volume) near zero.

This technique works best for continuous, low-frequency sound, like engine noise. It is not effective for impulse noise such as gunfire. (Click here for electronic hearing protection that works well for gunfire impulse noise.) For frequencies above 500 to 1000 hertz, passive hearing protection provides equal or better protection than active noise reduction. And at all frequencies, better protection is provided by passive ear muffs used in combination with ear plugs, and for a much lower cost.*

ANR hearing protection does have application in aviation and military environments, in conditions of extreme noise where speech communication is necessary — for example, by helicopter pilots, airport ground crew, and armored tank crew.

* E H Berger, "Active Noise Reduction (ANR) in Hearing Protection: Does it Make Sense for Industrial Applications?" (presented at the 27th annual conference of the National Hearing Conservation Association, Dallas, Texas, February 21–23, 2002).



See also:
Electronic hearing protection

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