SENNHEISER HMEC 45-CA Owner's Manual

Cover page of SENNHEISER HMEC 45-CA Owner's Manual

Owner's Manual for SENNHEISER HMEC 45-CA, downloadable as a PDF file.

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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
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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
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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:
Nervousness
Lack of concentration
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
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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 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 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®
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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Switching the Active noise compensation on and off
Inserting the batteries
The ON/OFF switch for the power supply of the NoiseGard® circuitry is located on
the battery compartment. When power is switched on, a green LED lights up.
When the power supply is switched off or when the batteries go flat the headphone
works like an ordinary headphone without noise compensation.
As the microphone is connected to the aircraft´s internal power supply, it does not
depend on the batteries and will remain in operation should the batteries fail.
on/off
LED
Cat. No. 03553
Hygiene pads (Accessories, not included in the scope of delivery)
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Adjusting the headband

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