Sennheiser NoiseGard HMEC 45-CA, HMEC 45-CAP, NoiseGard HMEC 45-KA Instructions For Use Manual
HMEC 45-CA
P/N 045-230-125
GEBRAUCHSANLEITUNG
INSTRUCTIONS FOR USE
NOTICE D‘EMPLOI
ISTRUZIONI PER L‘USO
INSTRUCCIONES PARA EL USO
GEBRUIKSAANWIJZING
HMEC 45-KA
P/N 045-230-115
140 dB Jet engine (at a distance of 25 m)
130 dB Aircraft engine (This is the treshold of pain)
120 dB Pneumatic drill
110 dB Blacksmith's Hammer, concrete works
100 dB Die-cast machine
90 dB Metal workshop
80 dB Tractor
70 dB Office
60 dB Conversation
50 dB Ambient noise
40 dB Living room
30 dB Library
20 dB Bedroom
10 dB Forest, no wind
The unit of sound levels is the decibel (dB). A noise reduction of 10 dB is generally perceived as halving of
the loudness, another 10 dB decrease corresponds to a loudness reduction of 75 %, and so on.
loud
quiet
The problem of noise
The negative effects of noise pollution have been proven by studies, and everybody
will have experienced them:
왘 Nervousness
왘 Lack of concentration
왘 Irritability
And these are only the most obvious effects on the human body. Noise also affects
the autonomic nervous system and can lead to permanent hearing damage.
There are a multitude of noise sources, and the individual very often has no
influence over them. The only solution when being in a noisy place is protecting
oneself against ambient noise. These noise problems are particularly prevalent in
an aircraft cockpit where a pilot often has to have the communications headset so
loud as to risk permanent hearing damage.
With the NoiseGard
®
system, Sennheiser has come up with an effective solution.
These operating instructions explain the NoiseGard
®
principle and show you how
to use the NoiseGard® headset.
Noise levels
HMEC 45-KA / HMEC 45-CA
A headset comprises two units, a headphone and a microphone. The HMEC 45KA/-CA headset is mostly used for communication in aircraft cockpits.
왘 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.
왘 The headphone is a Sennheiser NoiseGard
®
system. This is a dynamic
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 NoiseGard® compensation
circuitry in the headphone requires an extra power supply, so a battery compartment 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
®
increases your comfort,
but it is no medical hearing protection!
Active noise compensation with NoiseGard
®
100
200
500
1000
5000
2000
Frequency / Hz
0
10
Attenuation in dB
Human speech
Warning Signal
20
Reduction of the
subjectively perceived
noise level with
Noisgard
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