how do microphones in a phone not pick up any audio that the speakers put out? if I put a call on speaker mode, how do people on the other end not hear themselves?
In: Technology
One very important point – conferencing software never feeds the sound from your microphone back to your speakers. They feed that sound to everyone else, but never to you. This means you can’t get the short-loop feedback howl that is really easy to get in a PA. But you can get the long-loop warble from a loop that goes into your mic, out of someone else’s speakers, into their mic, back to your speakers, and to your mic.
Another thing they do is detect when you are speaking, and adjust the speaker volume down and the mic volume up, then restore the speaker volume and cut the mic once you stop. It doesn’t make for a good result, but it works.
You can also use a ‘comb filter’. Carve regular notches our of the speaker sound, so that a graph of the frequency response looks like a comb. Then filter the frequencies that remain in the speaker output, from the microphone, with a ‘complementary’ filter. The sound you get from such a setup is – well, ugly – but at least you can get rid of the worst echo.
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