Sounds like you're overthinking the problem. Add in pid or whatever if you're that worried - the pid's can be reused but you're not going to get the same pid and the same microtime unless the process takes less than 1 microsecond to run, which I highly doubt. Short of that, figure a way to sample ambient sound. Or you could always hit yourself in the face until your IQ lowers to a point where you aren't worrying about this any more.