SlackBuildsOrg/audio/listener

listener (listens for sound. If detected, it starts recording)

This program listens for sound. If it detects any, it starts recording
automatically and also automatically stops when things become silent
again.

In order to use this, a few steps need to be completed first:

1. Run setlistener (as an ordinary user), and use the
   cursor keys on your keybord to move the "|" left and right
   until <silence> appears in place of <SOUND!>. Make a note of the
   "Current detection level", and modify the detect_level value in
   /etc/listener.conf to match.

2. To start, run listener -f (to prevent it forking to the background.
   Omit -f if you wish to fork). Output will be saved in the current
   directory as an ogg file by default.