Play sound when silence in the room; stop sound when voices heard

Question

I need some guidance as I may have to shelve development until a later time.

I want to play a sound once the lights are switched off and the room goes dark, then stop the sound once the light is switched back on. I've discovered that Apple doesn't currently provide a way to access the ambient light sensor (not in any way that will get App Store approval).

The alternative I've been working on is to try and detect sound levels (using AVAudioPlayer/Recorder and example code from http://mobileorchard.com/tutorial-detecting-when-a-user-blows-into-the-mic/. I.e., when I detect voices of people in the room have dropped to a specific level (i.e. silence trying to compensate for background noise), I play my sounds.

However, if the people in the room start talking again and I detect the voices, I need to stop playing the sounds.

Q: is this self-defeating, i.e., the sound generated by the iPhone will essentially be picked up by the iPhone microphone and indistinguishable from any voices in the room? Methinks yes and unless there's an alternative approach to this, I'm at an impasse until light sensor API is opened up by Apple.

Answer 1

I don't think the noise made by the iPhone speaker will be picked up by the mic. The phone cancels sounds generated by the speaker. I read this once, and if I find the source I'll post it. Empirically, though, you can tell this is the case when you use speaker phone. If the mic picked up sound from the speaker that's an inch away from it, the feedback would be terrible.

Having said that, the only sure way to see if it will work for your situation is to try it out.

Answer 2

I agree with woz: the phone should cancel the sound it's emitting. About the ambient light sensor, the only alternative I see is using the camera, but it would be very energy inefficient, and would require the app to be launched.