Detecting Vibration on a Table with the iPhone

is it possible to d开发者_如何转开发etect vibration on the iPhone? I'm trying to figure out how to detect when the user smacks a desk or table when the phone is sitting on it. I remember reading somewhere you could detect a smack on a wooden table using the mic and AVFoundation. Any ideas?

Thanks

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if you go down the microphone route, something like this might do the trick:

//somewhere during setup call this line
[anAVAudioRecorder setMeteringEnabled:YES];

//then in a method used to poll the audioMeter
[anAVAudioRecorder updateMeters];
averagePower = [anAVAudioRecorder averagePowerForChannel:0];
if (averagePower > threshold ) {
    [musicPlayerClass play];
}