Sennheiser HMEC 305 MP3 Player Accessories User Manual


 
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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.