Noisegard Hmec 45-CA, Hmec 45-KA User Manual

GEBRAUCHSANLEITUNG
INSTRUCTIONS FOR USE
NOTICE D‘EMPLOI
ISTRUZIONI PER L‘USO
INSTRUCCIONES PARA EL USO
GEBRUIKSAANWIJZING

HMEC 45-CA

P/N 045-230-125

HMEC 45-KA

P/N 045-230-115

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
These operating instructions explain the NoiseGard

®

system, Sennheiser has come up with an effective solution.

®

principle and show you how

to use the NoiseGard® headset.

Noise levels

140 dB Jet engine (at a distance of 25 m)

loud

quiet

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.

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

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

Attenuation in dB

0

10

20

100

Reduction of the

subjectively perceived

noise level with

Noisgard

200

500

Human speech

1000

®

Warning Signal

2000

5000

Frequency / Hz