In my message, archived here
I mentioned that it seems that once a sound has played,
the image keeps sending silence to the sound device.

This keeps the CPU quite busy, as seen both by the OS
(load average) and the interpreter (slower benchmarks).

I've had a little more time to dig into this, and it
seems this is expected behaviour: it is toggled by the
"soundStopWhenDone" preference, and read in
SoundPlayer>>playLoop.  It seems that this is
off by default (i.e. sound never really stops, once
started). Switching it to "on" solved my problem.

So now I'm curious.  Why was it built this way?
And why do released images have this preference off?

For most modern hardware, this isn't an issue, but for
slower hardware (e.g. mine), or for power-lean systems
(e.g. the OLPC) I think it could be.