As we’ve mentioned in the previous blog, the technology of ANC headphones is all about generating "anti-noise" to cancel ambient noise. So correctly and precisely detects and analyzes the sound pattern of incoming noise are significant. It concerns the generation of the mirror "anti-noise" signal to cancel the ambiance noise out.
There are three kinds of ambient noise microphones implementation that Active Noise Cancellation headsets use nowadays.
Feedforward microphones means the microphones that used to collect ambient noise are placed outside the the ear cups. It is placed at the first place to "hear" ambient noise and the ANC accordingly generates a mirror "anti-noise" signal to cancel it out.
The outside microphones have more time to response to the ambient noise and generate the mirror noise. And this also means it's better at reducing high frequency noise up to 1-2 kHz. And it's the most affordable solution to block out commute noise. VA active noise cancelling earphones takes feedforward microphones that could effectively reduce the oppressive distractions on your commute.
The microphone only focus on the "outside" ambient noise. Cause it doesn't hear the reflected anti-noise, it couldn't help for self-correct and provide more precisely signals.
2. Feedback microphones
Feedback microphones are placed inside the ear cups. It hears the noise like our ear does.
The microphone could get the noise the listener get.
The feedback microphone doesn't have the effective performance as the feedforward microphone in reducing the noise in the 1-2 kHz range. And it may take income music as noise if not designed well.
3. Hybrid active noise cancelling
Hybrid active noise cancelling has both feedforward and feedback mics.
The two microphones could detects ambient noise more accurately. More over, it could cover a wider range of frequencies.
It costs twice! And two mics means more unwanted "white noise" generated and requires more expertise to get just right.
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