Sennheiser 250 Headphones User Manual


 
5
The HMEC 250 headset
The HMEC 250 headset with NoiseGard 2.0 active noise
compensation features closed, dynamic, circumaural stereo
headphones. The HMEC 250 is a headset for general aviation
use.
NoiseGard 2.0
The NoiseGard 2.0 active noise compensation system is
based on the principle of cancelling out sound using “anti-
sound” (phase-inverted sound). Tiny microphones pick up
low-frequency ambient noise (up to 1 kHz) near the ear. The
NoiseGard 2.0 electronics use this noise to generate a sound
wave which is the exact opposite (i.e.: at the same level but
polarity reversed – 180° out-of-phase), the result is that the
polarity reversed signal cancels most of the outside noise.
Fail safe operation
When the batteries are completely discharged, the
NoiseGard 2.0 active noise compensation automatically
switches off. RT traffic (e.g. ATC) and intercom will still be
heard through the headphones.
Peak level protection
The peak level protection safeguards your ears from volume
peaks above 110 dB.
HMEC250_516578_0507_SP6.book Seite 5 Mittwoch, 13. Juni 2007 3:18 15