So, if I’m in a call with someone, with the speaker on, why does the mic not receive the sound the phone is emitting?
In: Technology
The simplest systems just turn off the speaker when the microphone is in use and turn off the microphone when the speaker is on.
More modern systems use signal processing algorithms to filter the sound from the speaker out of the microphone signal.
The gain on the microphone may be set for speech — it detects speech, but not a lot of outside sounds. You may be able to increase the ‘gain’ setting in the audio controls to detect other outside sounds, if that’s what you want.
That lower ‘gain’ setting is to prevent a lot of extra unnecessary noise — but if you’re in a quiet setting and want to detect other sounds, you can turn it up.
The phone (or computer that’s doing the video/audio conferencing) has software that knows what signals it just sent to the speaker, and uses those signals to cancel out the speaker’s sound that’s coming in through the microphone. The remaining signal picked up from the microphone is your voice, which the software can send to the other end of the call. This is the sophisticated approach to preventing the speaker’s sound from interfering with your voice.
As someone else already pointed out, a simpler approach is to mute the speaker when the phone detects sound is coming in through the microphone. This is a pretty good technique (not a great one), but it’s a lot cheaper to make than the signal analysis and cancelling that’s done in the sophisticated technique.
the *simplest* method? you have one audio waveform from the speaker. you have a second from the microphone. you simply remove one from the other…
So the waveform being sent out, is what the microphone is hearing, with what the speaker is playing subtracted from it.
the speaker is playing the incoming wave form with what the microphone is hearing subtracted from it.
That’s why old Nokia phones had the microphone in the speaker cup.
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