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audioaudio-recordingvolume
Qiao Zhang
Qiao Zhang

Reputation: 589

Compare the volume of two audio files

I want to test the performance of a hand-made microphone, so I recorded the same audio source with or without the microphone and got two files. Is there a way to compare the volume of two files so that I know the mic actually works?

Could the possible solution be a package in Python or Audacity?

Upvotes: 0

Views: 2155

Answers (1)

Igid
Igid

Reputation: 515

You will want to compare by loudness. The minimally accurate measure for this is A-weighted RMS. RMS is root-mean-square, ie. the square root of the mean of the squares of all the sample values. This is significantly thrown off by low-frequency energy, and so you need to apply a frequency weighting. The A curve is commonly used.

The answer here explains how to do this with Python, though it doesn't go into detail on how to apply the weighting curve: Using Python to measure audio "loudness"

There doesn't seem to be a built-in function to do this with Audacity, but viable plugins might be available, eg: http://forum.audacityteam.org/viewtopic.php?f=39&t=38134&p=99454#p99454

Another promising route might be ffmpeg, but all the options I found either normalise or tag the files, rather than simply printing a measurement. You might look into http://r128gain.sourceforge.net/ (it uses LUFS, a more sophisticated loudness measure).

Update: for a quick and dirty un-weighted RMS reading, looks like you can use the following command from https://trac.ffmpeg.org/wiki/AudioVolume :

ffmpeg -i input.wav -filter:a volumedetect -f null /dev/null

This question might be best migrated to Sound Design Stack Exchange.

Upvotes: 3

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