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I'm looking to calculate the loudness of a piece of audio using Python — probably by extracting the peak volume of a piece of audio, or possibly using a more accurate measure (RMS?).

What's the best way to do this? I've had a look at pyaudio, but that didn't seem to do what I wanted. What looked good was ruby-audio, as this seemingly has sound.abs.max built into it.

The input audio will be taken from various local MP3 files that are around 30s in duration.

Sam Starling
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    PyMedia provides a [`getVolume`](http://pymedia.org/docs/pymedia.audio.sound.html#Output-getVolume). – Hank Gay May 29 '11 at 21:37

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I think that the RMS would be the the most accurate measure. One thing to note is that we percieve loudness differently at different frequencies, so convert the audio to frequency space with an fft (numpy.fft should work great on only 30s of audio). Now compute a power spectral density from this. Weight the PSD by frequency using some loudness curve. Especially frequencies below 10Hz, since there will be a lot of power there (it would dominate the RMS calculation in the time-domain), yet we can't hear it. Now integrate the PSD and take the square root and that will give a percieved RMS.

You can also break the mp3 into sections or windows and apply this technique to give the volume in particular sections.

Lee McCuller
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