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
This has probably been said but I’m too lazy to scroll through the comments. On an iPhone, when you’re listening in the earpiece, there’s a microphone enabled on the bottom of the phone by your mouth (and bottom speaker). If you enable speaker mode, that bottom mic disables and it enables a mic that’s built into the earpiece so it doesn’t hear the speaker blasting right next to it
The correct answer is:
Acoustic Echo Cancellation or AEC.
The phone has 1 “channel” of AEC. This is the technology which “cancels out” the audio from the speaker.
Electronic engineer here
Sound’s system in phones has something called “negative feedback loop”
which basically means that it subtracts the output sound from the inputs sound.
here is what it does in a function form
(person voice + phone voice) – **(phone voice from feedback loop)** = person voice
the bold **phone voice** is the signal fed through by the negative feedback loop.
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.
I mean, I can definitely hear when someone has me on speaker. And I can definitely hear myself talking.
Just throwing this out there, as someone who works in a call center taking for 8 hours to people in their cellphones, your speakerphone doesn’t filter out sounds as much as you think. Please, just take the call off speaker. I’m so tired of hearing myself echo back.
As someone who works in a call center, a lot of speakers do pick up their own audio on speakerphone, and the person DOES hear themselves. And we hate it.
I’m a tech support specialist for a major phone company, and I can tell you the phone company uses algorithms in the transport network to combat feedback and reduce outside noise on phone calls. Much of it is done in the network, not by your phone. That said, it’s not perfect, and if you’ve ever sat on a large conference call you know speaker phones do feedback. I hear my own voice echo, I hear everything in the background. The most annoying are people who eat while they’re on the phone and loud mouth breathers
Part of my job is taking calls from the public. I can hear everything going on in the background and I wish people didn’t think phones were a magic device that only picked up speach. I can hear you eating, peeing, breathing. I can hear Wheel of Fortune in the background. I can hear the baby screaming on your lap. If you put me on speaker phone I do hear an echo of everything I say.
If you call someone be courteous and do it from a quiet place.
In modern Cellphones, they’ve taken to being half duplex, so while the speaker is outputting noise, the microphone is turned off, and when the microphone is listening, the speaker is cut. This is why you can’t talk over each other on a cellphone and still hear what the other person is saying like you could on analog phones years ago.
There might be some magic software or hardware witchery on some types of connection, but the cell companies are too cheap to put full duplex systems in for everyone.
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