Acoustic Noise Cancelling headphone technology is a method of
reducing unwanted noise by electronically creating a signal that is the
mirror image of the unwanted noise. Microphones in the earcups monitor
sound at the user’s ear and externally. The monitored sound (music and
noise) is compared to the sound the user wants to hear (the signal coming
from the audio input – this could be music or silence). The difference
between the monitored sound (from the earcup’s microphone) and the
sound the user wants to hear (music or silence) is noise. The electronics in
the QuietComfort 25 Acoustic Noise Cancelling headphones instantly
process the noise signal, and a precise equal and opposite signal
(correction signal) is created. This opposite signal is then sent to the
speaker in the earcup along with the sound the user wants to hear (again,
this could be music or silence). The result is three signals being presented
to the user’s ear:
1. Noise (monitored by the earcup microphones) from the environment.
2. The sound the user wants to hear (music or silence) from the audio
input.
3. The correction signal from the system electronics.
The noise and correction signal nearly cancel each other (1 + -1 = 0),
providing a clean, high-fidelity sound signal at the ear.
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