Reduce noise from other z-levels

[nornagon]

Closes #14123.

[Coolthulhu]

20 is quite a lot. I was thinking more like 5 or so.
10 would be a good compromise - it would prevent hearing moving ants, but not hulks stomping around, glass breaking etc.

[nornagon]

Updated to 10.

[nornagon]

Rationale [copied from #14123]:

Since the sound code doesn't take into account any terrain at all, there's not any obvious place to differentiate between "an NPC on the 2nd floor of a building with an open window" and "a soldier ant with 6 feet of dirt between it and the surface".

Given almost all sounds from another level right now are in the latter category, more or less, would it make sense to simply count each Z level difference between the source of the sound and the player as something like 20 tiles of X/Y distance?