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
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
Hygiene pads (Accessories, not included in the scope of delivery)
Cat. No. 03553
Adjusting the headband
350°
Cable (worn on left or right side)
Cable on the left
N.B.: NoiseGard
NoiseGard®
Cable on the right
®
reduces noise and increases comfort.
is not a medical noise protection
system!
NoiseGard®
cannot replace an industrial ear
defender system for use in noisy environments!
volume up? - No !
When people use headphones, they tend to choose a higher volume than with
loudspeakers. Listening with high volume levels for a longer time can lead to
permanent hearing defects. Because the NoiseGard® circuitry is reducing the
ambient noise the headphones can be set at a correspondingly lower level leading
to more comfortable hearing conditions so protecting your hearing.
Circuit diagram and pin connections HMEC 45-KA
microphone
rd
bl
screen
sensor
microphone
screen
bl rd or wh br gn ye
cable splice
bl rd ye bl bk
screen
Tip
PJ–068
microphone
headphone capsule left
left
Tip
PJ–055
headphone
headphone capsule right
sensor
microphone
right
bl
rd
screen
rd
DC-box
bl
Circuit diagram and pin connections HMEC 45-CA
microphone
screen
bl rd
screen
bl rd ye bk
headphone capsule left
rd
bl
screen
sensor
microphone
left
cable splice
or wh br gn ye
XLR 5
rd
bl
bl
rd
screen
headphone capsule right
sensor
microphone
right
DC-box
Technical data NoiseGard
®
HMec 45-KA / -CA
Headphone
Transducer principle dynamic, open
Frequency response 20 Hz - 18 kHz
Impedance active 600 Ω (mono) 1.2 kΩ per side (stereo)
passive 160 Ω (mono) 320 Ω per side (stereo)
same volume for active and passive
THD < 1 %
Active compensation 10 dB ±3 dB between 400 Hz and 1 kHz
Mikrophone incl. preamplifier
Transducer principle Noise-cancelling back-electret condenser
microphone capsule
Frequency response
(2 cm distance between mic
and corner of mouth) 300 Hz - 5 kHz
Max. sound pressure level 120 dB (THD 1 %)
Output voltage 400 mV ± 3 dB at 114 dB SPL
(as per RTCA/DO-214)
Terminating impedance 150 Ω
Operating voltage 8 - 16 V DC, 8 - 25 mA
connections as per RTCA/DO-214
General Data
Contact pressure approx. 1.6 N
Weight without cable 140 g
Cable single-sided, total length 1.8 m
Connectors HMEC45-KA headphone: PJ-055, 6.3 mm (1/4")
microphone: PJ-068, 5.25 mm
HMEC45-CA XLR-5
Power supply 2 x 1.5 V AA type alkaline-manganese batteries
or 2 x 1.2 V AA type rechargeable batteries,
600 mAh
Operating time batteries: approx. 80 hrs
rechargeable batteries: approx. 20 hrs
Display green LED for indicating battery
and noise compensation status
Supply schedule 1 HMEC 45-KA or HMEC 45-CA
Subject to alterations.
Aktuelle Informationen zu Sennheiser-Produkten erhalten Sie auch im Internet
unter „http://www.sennheiser.com“.
Up to date information on Sennheiser products can also be found on the Internet
under “http://www.sennheiser.com”.
Vous trouverez également toutes les informations actuelles relatives aux produits
Sennheiser sur Internet, sous “http://www.sennheiser.com“.
Informazioni attuali sulla gamma di prodotti Sennheiser sono disponibili anche in
Internet al sito „http://www.sennheiser.com“.
También en Internet, bajo „http://www.sennheiser.com“ obtendrá Vd.
informaciones actuales sobre los productos Sennheiser.
Actuele informatie met betrekking tot Sennheiser producten vindt u ook op
Internet onder “http://www.sennheiser.com“.
Sennheiser electronic GmbH & Co. KG Telefon: 05130/600-0
D-30900 Wedemark Telefax: 05130/600-300
Printed in Germany Publ. 4/98 59887 / A03
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