It has been posited that it doesn't make sense to hear certain sounds through walls. So, I proceeded to go and change that.
All sounds with a volume of 50 or less will now be played only to the "hearers" list. This is basically people within line of sight. I also rewrote the lower levels of the sound API with this. The code is now more modular, while retaining the same main API entry point playsound.
This needs a test merge to see how badly I broke shit.