Filter
Top Products
29
NoiseGard active noise compensation is achieved by generating a signal identical in
sound pressure level but exactly reversed in phase to the noise signal, the effect being
that the out-of-phase signal cancels most of the noise signal.
Active noise compensation is accomplished in the following manner: Each earcup
includes a microphone, a feedback control circuit, and a transducer to reproduce both
the communication and the noise cancelling signal. The feedback control microphones
sense the total sound pressure within each earcup resulting from both the desired radio
signal from the receiver and the undesired noise that has come through the earcup. The
microphone signal is amplified and the radio signal is subtracted from it. The remaining
signal (noise) is then filtered and inverted and the radio signal is added back in.
Eventually, the entire signal is amplified and fed back to the transducer in each earcup.
Since the noise component of the signal is inverted, it cancels the noise signal coming
through the earcup. The radio signal remains unaffected, as it was not processed
through the cancellation circuits.
The diagram on the left shows noise compensation with NoiseGard: Passive hearing
protectors effectively attenuate noise from the middle and upper frequency range, the
effect decreasing sharply in the lower range. However, active noise compensation with
NoiseGard combined with passive hearing protectors results in a reduction of noise of
approx. 25 dB in the 25–500 Hz frequency range. The total attenuation resulting from
active and passive noise compensation is about 30 dB over the entire audio range.
A 10 dB reduction in noise is perceived subjectively as a halving in volume. A further
reduction in noise of 10 dB again results in a decrease in unwanted noise by 50 %.