/etc/init/sound-device.conf

start on (sound-device-changed SOUND_INITIALIZED=1 KERNEL=card0) and (sound-device-changed SOUND_INITIALIZED=1 KERNEL=card0) and (sound-device-changed SOUND_INITIALIZED=1 KERNEL=card0)
stop on (sound-device-removed KERNEL=card0) or (sound-device-removed KERNEL=card0) or (sound-device-removed KERNEL=card0)

pre-start script
true
end script

post-stop script
true
end script