The last device, still in development, will solve the same museum problem as our motion detector solution but from a different approach.  It will use a microphone to detect ambient levels of audio. It will smoothly drive audio levels up and down to the next level based on crowd noise.  Although more elegant, this is a much more difficult solution and might not be applicable to all environments as the motion detector.  To date, this has proven to be the more difficult variant and we are still working the algorithm and microphone combinations needed to reliably solve this problem.