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Reduction of subjectively perceived noise level
NoiseGard
™
are dynamic stereo headphones which, in addition to transmitting an
audio signal, also electronically compensate low-frequency noise. This active noise
compensation functions according to the physical principle that noise and „anti-
noise“ (exactly reversed in phase) cancel each other out.
So, now you can enjoy your music undisturbed, without having to turn the volume
up so high that surrounding noise is completely drowned out.
The
NoiseGard
™
compensation electronics in the headphone requires its own power
supply. This is provided by the power supply unit which is fixed to the cable.
The headphone is connected in the usual manner by a 3.5-mm stereo jack plug, by
an adapter to two 3.5-mm mono jack plugs (in aircraft) or by means of a 6.3-mm
adapter (to the hi-fi unit at home). Both adapters are supplied.
Noise compensation with NoiseGard
™
ON/OFF
LED
NoiseGard
™
HDC 451
The first „open-air“ stereo headphone with
NoiseGard
™
active noise compensation
At just 110 g, this „open-air“ stereo headphone with active noise compensation is
extremely light and provides excellent wearer comfort. Sound coupling to the ear
is directly on the ear.
̈ When you are wearing the NoiseGard
™
HDC 451 you will still be able to join
in conversation - the voice of the person talking to you is scarcely changed,
since the speech frequency is practically unaffected by compensation.
̈ Warning or emergency signals remain audible.
̈ Understanding speech is even improved by NoiseGard
™
, as „upward-masking“
by low-frequency sound is eliminated.
Switching ON/OFF
ON/OFF switch for the power supply to the compensation electronics is situated
on the battery box. A green LED lights up as a check.
If the power supply is switched off or the batteries are worn out, the headphone
can still be used as a normal headphone without noise compensation.
Inserting the batteries in the power supply unit
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
HDC 451 12.07.2002, 13:21 Uhr8-9