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

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)

Adjusting the headband

350°

Cable (worn on left or right side)

Cable on the left

Cable on the right

N.B.: NoiseGard

®

reduces noise and increases comfort.

NoiseGard®

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.

Tip

PJ–068

microphone

Tip
PJ–055
headphone

microphone

headphone capsule left

sensor

microphone

left

headphone capsule right

screen

screen

bl

rd

bl

rd

screen

rd

bl

screen

cable splice

bl rd or wh br gn ye

bl rd ye bl bk

DC-box

sensor

microphone

right

Circuit diagram and pin connections HMEC 45-KA

XLR 5

microphone

headphone capsule left

sensor

microphone

left

headphone capsule right

screen

screen

bl

rd

bl

rd

screen

rd

bl

screen

cable splice

bl rd

or wh br gn ye

bl rd ye bk

DC-box

sensor

microphone

right

Circuit diagram and pin connections HMEC 45-CA

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.

Sennheiser electronic GmbH & Co. KG Telefon: [phone]
D-30900 Wedemark Telefax: 05130/600-300

Printed in Germany Publ. 4/98 59887 / A03

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