xbevd, a simple X bell event daemon (based on xbelld & nxbelld).
Compile with gcc -Wall -O2 xbevd.c -o xbevd -lX11 and put the executable into your PATH.
The program listens for X bell events and prints DISPLAY and the milliseconds since EPOCH to stdout.
Example usage:
#!/bin/sh
soundfile="/usr/share/sounds/freedesktop/stereo/complete.oga"
timeout=500
[ -f "$soundfile" ] || exit 1
lastbell=0
xbevd | while read -r disp time; do
if [ $(( time - lastbell )) -ge $timeout ]; then
( /usr/bin/ogg123 -d alsa -o dev:hw:0 -q "$soundfile" & )
lastbell=$time
fi
done