I tried to find a Linux solution to automatically record scanner traffic, something like Scanner Recorder for Windows. It looks like I am not alone. Anyway, I figured it out.

This is how I did it under Ubuntu:

1. Download xpvox here.
2. Compile it (I had to install libforms and then change all instances of #include "forms.h" to #include <X11/forms.h>).
3. Install speex.
4. Make sure /dev/dsp0 exists (if not, mknod /dev/dsp0 c 14 3).
5. Run xpvox -ios | speexenc -V --rate 44100 - out.spx.

After you quit xpvox, you’ll find a file called out.spx which contains all recorded traffic, with silent bits cut out.