On a MacBook, I can be in a Zoom Meeting and speak into the MacBook Mic, while also listening to the meeting via the MacBook speakers. How is it possible for the mic to only receive my voice (and not also the sound of the meeting coming out of the speakers)?
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Devices “know” what audio is being outputted through their speaker and will how the sound from the speakers is picked up by the mic, and will cancel out the audio output from the device that the onboard mic picks up.
A lot of people have commented about the Macbook being the primary device here. You can 100% create feedback with a macbook microphone, Zoom is doing more of the heavy lifting when it comes to noise cancellation. I’m an audio engineer who works in live events that utilizes Zoom for remote presenters and it amazes me how well Zoom accomplishes this.
The Distance between the microphone and the speaker is constant, and the speed of sound through all relevant media is also known, *and* the sound is known.
You can use that to know exactly when feedback from the speakers should hit the microphone, and remove it.
Going off the other replies, when 2 people on a call are watching the same livestream (and both are using speakers), the laptop will naturally cancel out the sound of the speakers. However, when there’s another source of audio being picked up on top of the speakers (such as someone talking),the frequencies of the speaker audio tend to slip through the cracks and you can hear little bits.
That’s why on virtual meetings you can hear someone’s laptop speakers only when they’re speaking
TL; DR
Laptop cancels out the audio, but it has trouble cancelling the sound of your speakers if there is another source of sound in the room, like you speaking.
As others have said, this is done electronically.
But I’d like to point out that there’s also a mechanical way of doing something similiar to get a directional microphone. You simply leave the back of the microphone open. This way, ambient noise will press on the microphones membrane from all sides, and cancel out.
But if you speak to one side of the microphone, those sound waves will only push on ine side of the membrane and be detected.
This question reminds me of trolling full chats on fb messenger with 2 accounts one on a phone and one on laptop. I would place my phone speaker above my laptop speaker and when anyone spoke or made any noise a crazy amount of reverb was made, to the point the chat was broken and constantly piping out the same reverbed almost bagpipe sounding drone.
I’d like an ELI5 on how M1 MacBooks can have a faulty sound output (incessant crackles) and it not need a recall- or even have a fix!
The speakers are not very loud, and are positioned away from the microphone, which is not of high sensitivity or wide bandwidth.
I can get a mac to feed back with plugins or just boosted gain… very easily.
Echo cancellation processing my friend. It’s magic. The computer at the far end is actually the one doing the work for you while your computer is doing the work for the person your on a call with. And so the end result is a solution for both parties.
The audio passing to your speaker is used as a reference and digitally removed if it is detected in your mic feed so the far end does not hear themselves back. The way this algo works is beyond me but I bet someone here will explain it in simple terms. If I had to guess the audio would be inverted and the two waves would the be added together. This creates a canceling effect.
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