I have a 2018 MacBook Pro running Mojave. Midway through a Zoom meeting, people were suddenly not able to hear me. I checked System Preferences and saw that my internal microphone was selected as the input, but it wasn't picking up my voice (though it picked up the sounds of me typing or tapping). After turning my input volume to max and disabling ambient noise reduction, I was still only barely audible.
I have tried resetting my PRAM and SMC, but to no avail. Any help would be greatly appreciated.
Best Answer
It sounds like a hardware failure, however if you have the ability create a boot drive for yourself and try starting up off the fresh volume to test the microphone, that would be ideal.
If you don't have a boot drive ready yet, you can try creating a test user account to try the microphone under.
Check the drive using disk utility, just in case as well.
I have a faulty microphone on an iPad that acts the exact same way -- physical taps and bumps will be picked up but nothing standard. I suspect the microphone unit fell out of place, something shorted out, or something physical damaged it.