I have a hydraulic breaker on a excavator that hammers with a dynamic bpm. I have recorded this sound so that it is in a mp3-file and would like to determine the momentary bpm for the length of the file.

I have tried using processing with beat detection from the minim-library but so far without any good results.

Is using beat detection with energy mode in a selected band the preferred way to go? I have had troubles getting good information about where, in terms of frequency, the beats are.

An example of the sound could come from http://www.youtube.com/watch?v=596Dtm95Txo