Hi Matthew, thanks for taking the time! Yes, the delay is definitely set correctly (see screenshot).
The problem is, the sound is played for its whole duration of 4 seconds and does not fade out at all (first I assumed the fade out is working, but when I remove it, it doesn’t sound different). I want it to fade out after the 1.5 sec delay (that’s when the battery pickup is destroyed) and stop playing after it faded out. As my sound is 4 seconds long but should end after 1.5, I’m fairly sure the fade out is not working as I intend it to. 
Am I doing something conceptually wrong here, a fade out should pre-emptively end the sound playback, shouldn’t it?