Sennheiser NoiseGard HMEC 45-CA Instructions For Use Manual page 3

HMEC 45-KA / HMEC 45-CA
A headset comprises two units, a headphone and a microphone. The HMEC 45-
KA/-CA headset is mostly used for communication in aircraft cockpits.
The microphone is a high quality back-electret condenser microphone. As per
TSO / ARINC it receives its operating voltage via a connector from the
aircraft´s internal power supply.
The headphone is a Sennheiser
headphone system which, in addition to reproducing the original audio signal,
electronically cancels the low frequencies of the ambient noise. This active
noise compensation operates on the principle that sound and „anti-sound" (in
phase opposition) cancel each other out. The
circuitry in the headphone requires an extra power supply, so a battery com-
partment has been integrated into the headset cable (see illustration on the right).
Clearly intelligible communication is ensured, and the pilot no longer has to
turn the volume up to overcome ambient noise.
®
NoiseGard
but it is no medical hearing protection!
Active noise compensation with NoiseGard
Attenuation in dB
0
10
20
100
increases your comfort,
Reduction of the
subjectively perceived
noise level with
Noisgard
200
500
NoiseGard
®
Warning Signal
Human speech
1000 2000
system. This is a dynamic
®
®
NoiseGard
5000
compensation
Frequency / Hz