Why does my zoom audio, when there are nearby microphones, seem to usually take an open loop format? The signal from the speaker on device A gets into the microphone from device B, then the amplifier and then the speaker from device B, back into device A. The result is a sort of runaway signal that is always reamplifying itself?
Why can't I create a sort of closed loop system when I have nearby microphones? What would I need to do? What gear and/or software would I need to create a closed feedback loop?
This effect is usually undesirable and is prevented by (acoustic) echo cancellation algorithms. These algorithms estimate the distortion of the incoming signal on its way to the microphone (via the loudspeaker and the room acoustics). That distortion is modeled by a filter and the output of that filter is subtracted from the microphone signal, such that the contribution of the incoming signal to the outgoing signal is minimized.
Zoom has an option to turn off echo cancellation, so you could try playing around with that.