Can I query which processes (if any) are currently accessing the microphone?

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http://www.linuxquestions.org – I'm running Debian (technically Raspbian), trying to get a Star-Trek style voice-command system. I've got it mostly up and running, but in the interests of privacy and all that jazz, I don't want my microphone always recording. I'm wondering, is there a way to poll which processes, if any, are currently accessing the microphone? The idea is that I'd make myself a little indicator to tell if the microphone was currently recording audio or not. My ultimate goal is to turn the microphone on and off using a TV-remote, and to have an LED indicator for if it's on or off. I've got all the hardware (HowTos)