eli5: What is happening when you put a microphone up to speaker it is connected to?

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Edit: Vibrationally what is happening? What would it look like in waveforms?

I’m wondering because it’s the closest thing I can think of that represents an auditory paradox. And I’m curious what that would look like.

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2 Answers

Anonymous 0 Comments

The speaker is playing the first sound the microphone picks up, then the microphone picks up the sound the speaker plays. This loop happens over and over causing the sound to get louder and louder

Anonymous 0 Comments

It’s not a paradox, it’s a feedback loop.
The microphone goes into an amplifier which boosts the signal, then the amplifier powers the speaker which plays that boosted signal louder than the original.
If you hold a microphone into a speaker it just boosts the signal in a loop indefinitely until the amplifier can’t make it any louder.

It squeals and howls because microphones and speakers are not perfect and they emphasize certain frequencies louder than others, so when you make a feedback loop, those frequencies get boosted most and you end up with loud squealing.

Also, don’t do it intentionally. It can be really bad for the microphone, speaker and all the electronics in between.