If too many of these sounds are started in one frame (for example if the
player shoots with the super shotgun into the power screen of a Brain)
things get too loud and OpenAL is forced to scale the volume of several
other sounds and the background music down. That leads to a noticable
and annoying drop in the overall volume.
Work around that by limiting the number of sounds started. 16 was
choosen by empirical testing.