Sometimes even if only one of the phones’ mic is on.
In: Technology
Imagine you and a friend are playing “instantly repeat what the other person says” After a few seconds, you’ll be screaming at each other.
Phones and video conferencing apps have to work really hard to deal with feedback. The speakers make noises, the microphones, in the same box as the speakers, try to pick up sounds outside while not being swamped by sound coming from the speaker.
They pull all sorts of tricks to make this work, but the most important is never sending the sound you are making back out through your speaker. This prevents a feedback loop, where the sound coming out of your speakers is picked up by the microphone, and send back out through your speakers again, is picked up by the microphone, etc.
But if you have two devices close together, the system sends sound from your microphone to the other phone’s speaker, where it finds its way back to your microphone again. It can’t cope with this.
Similar problems happen when two devices on the same call have local feedback problems. Sound from you goes out of his speaker, is picked up through his microphone and sent back to your speaker, where it is picked up by your microphone. This shows up as a person’s long vowel sounds being clipped, a person sounding robotic, or someone’s volume going up and down randomly. It can even sound like connection problems.
Feedback is the reason why the first rule of conferencing is – if at all possible, use a headset. Sound coming out of headphones can’t find its way into a microphone, saving everyone a lot of trouble.
The weird sounds are a result of feedback. When a sound is made nearby two phones that are on speaker, phone one is producing a sound (output) and its being received by the second phones input. The second phone then reproduces the sound through its output which is then received by the first phones input. The cycles continues in a feedback loop, as each output reproduced increases the amplitude of the signal. The signal is broken when the sound either is too quiet to be picked up by an input or if any part in the loop (input, output, input, output, etc.) is broken.
Feedback. The same soundsource is „heard“ and „played“ at the same time. The same issue occurs when the microphone is getting too close to the speaker. It’s a feedbackloop. The sound from the speakers go into the mic and come out of the speakers and go into the mic again…
This is called feedback and is similar to what happens if you put live microphone near a speaker connected to it.
Microphone on one phone picks up a sound, then the other phone plays that sound and the first phone picks it up again and amplifies it in an continuous loop ultimately causing a high pitched noise.
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