Sennheiser HMDC 322 Service Manual download pdf (Page 64)

Valuable information on NoiseGard™

The NoiseGard™ principle

One of the greatest stress factors today is noise. Research has shown that noise affects

the nervous system, and can cause tiredness, poor concentration, irritability and tension.

Of even greater concern is the permanent damage to hearing that can result from noise

at high levels.

This problem concerns pilots in particular. Cockpit noise amounts to about 80 dB(A) in

jets and to 90 up to 97 dB(A) in turboprops. During takeoff and landing, the noise level

is even higher. To be able to understand radio traffic in spite of the noisy environment,

the ATC signal level must be set to at least 95 dB(A). Permanent hearing loss caused by

the continuous noise in aircrafts is the reason why many pilots became prematurely

disabled or lost their pilot´s license.

Circumaural communication headsets provide noise attenuating properties and are

commonly used to address this problem. However, the noise attenuation of these

headsets is uneven. High frequencies are reduced considerably, but low frequency wind

and engine noise, the most prominent noise in many of today's aircrafts, is attenuated

very little.

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Sennheiser HMDC 322 Service Manual Page 64