Tracker, Meet AudioXPlorer

I’ve been noticing more and more people using the awesome free program Tracker for video analysis. But what about audio analysis? I’m teaching the third quarter of physics soon (waves, optics, and thermodynamics), and have been looking for ways to get students to do some basic acoustical measurements and processing. Clearly they’ll need some software. Is there any free stuff of the same caliber as Tracker? By which I mean:

  1. It has to be free.
  2. It should work on a PC or Mac. Both, preferably, since I use a Mac at home and PC in the classroom.
  3. I’m looking for something that can take sound from internal and external mikes and from audio files.
  4. I need to at least be able to see a sound’s waveform (i.e. microphone voltage vs. time), spectrum (power spectral density vs. frequency), and something like a periodogram (sometimes called “spectrograms” – spectra through time).

I found a nice little list of candidates here, though not all are exactly what I’m looking for. I’ve been testing two packages – Spectre and AudioXPlorer. Both only work on Mac, so I’m not 100% convinced that either of these will be the way to go. Spectre is not free, which disqualifies it on that front, but at least it has a 15-day trial period. So far, it seems that both meet my requirements as far as inputs and outputs. Spectre seems to have a few bugs that cause problems as it quits. AudioXPlorer (screenshot below) seems to work much more smoothly.

Screenshot of AudioXPlorer showing waveform, spectrum, and spectrograph windows.

Screenshot of AudioXPlorer showing waveform, spectrum, and spectrograph windows.

I’m hoping to use the software to illustrate the frequency content of certain waveforms (e.g. square waves, tuning fork, human voice), the relationship between pitch and spectrum, overtones, beats, and possibly dispersion (I’m working on a way to do that…). I think computer demos and activities will be much more fun than some of the standard oscilloscope-based demos, though I’m going to do some of the latter too. Any ideas, both on software and activities¬† would be much appreciated.