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
They do, and it is very difficult to mitigate.
The first step is to isolate the speaker and the microphone from the chassis, as sound is a vibration and the chassis will transmit it better than air. Ths is mechanical engineers job, and it is not easy, esp. on a cramped cell phone.
The next step is to use specific microphones that are directional, and will only pickup sound from a very near source.
Then there is active noise cancellation, where a secondary (or more) microphone records the ambient noise to “substract”it from the one coming from the primary microphone. This is done by software.
Finally, there are various filters, both software and hardware, to eliminate unwanted noise, like echo and larsen. some are integrated in chips, others need to be coded. People often use both.
TL;DR: the microphone picks this up, but phones are made to remove it.
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