Some level scripts in d3xp (erebus4, erebus4, phobos2) use
$entity.startSoundShader( "", SND_CHANNEL_BODY );
(or whatever channel) to stop the sound currently playing there.
With s_playDefaultSound 1 that results in a beep..
Added a special case to that event implementation to call StopSound()
instead when the soundName is "" (or NULL)