How to detect microphone usage on OS X?

Question

Is there a way to detect when the microphone of my Mac is in use? Similar to what Mikro Snitch does? Can this be done in Cocoa?

Answer 1

This isn't really an Objective-C or Cocoa solution, but if you're willing to do a subprocess call, try this:

ioreg -c AppleHDAEngineInput | grep IOAudioEngineState

You will see "IOAudioEngineState" = 1 when audio input is active.

Also, try searching for IOAudioEngineNumActiveUserClients which increases by one for each app taking in audio.