I need to monitor my audio line-in in linux, and in the event that audio is played, the sound must be recorded and saved to a file. Similiar to how motion monitors the video feed.

Is it possible to do this with bash? something along the lines of:

#!/bin/bash

# audio device
device=/dev/audio-line-in

# below this threshold audio will not be recorded.
noise_threshold=10

# folder where recordings are stored
storage_folder=~/recordings

# run indefenitly, until Ctrl-C is pressed
while true; do
   # noise_level() represents a function to determine
   # the noise level from device
   if noise_level( $device ) > $noise_threshold; then
     # stream from device to file, can be encoded to mp3 later.
     cat $device > $storage_folder/`date`.raw         
   fi;
done;