I have a big MP3 - 508MB (its 8 hours long)

2. I would eventually like to see a waveform of the entire file. I can in Audacity and I can see that there are three significant sustained amplitude increases (audio is taken form a restaurant, so breakfast, lunch and dinner time). I would like to use the waveform to drive a vibration motor (im using Arduino for this). But instead of 8 hours, I want the waveform compressed into about 3 seconds. How do I get this waveform data in Minim? How do I compress it into 3 seconds? Am I making any sense?