Adds area soundproofing. (#7881)

* Adds area soundproofing.
Areas now have a var for soundproofing in order to block sounds from other areas from entering or sounds from within leaving the area.

* Update sound.dm

* Update sound.dm

code/game/area/areas.dm

@@ -50,6 +50,7 @@
 	var/turf/base_turf //The base turf type of the area, which can be used to override the z-level's base turf
 	var/forbid_events = FALSE // If true, random events will not start inside this area.
 	var/no_spoilers = FALSE // If true, makes it much more difficult to see what is inside an area with things like mesons.
+	var/soundproofed = FALSE // If true, blocks sounds from other areas and prevents hearers on other areas from hearing the sounds within.
 
 /area/Initialize()
 	. = ..()
@@ -367,9 +368,9 @@ var/list/mob/living/forced_ambiance_list = new
 	// Ambience goes down here -- make sure to list each area seperately for ease of adding things in later, thanks! Note: areas adjacent to each other should have the same sounds to prevent cutoff when possible.- LastyScratch
 	if(!(L && L.is_preference_enabled(/datum/client_preference/play_ambiance)))
 		return
-	
+
 	var/volume_mod = L.get_preference_volume_channel(VOLUME_CHANNEL_AMBIENCE)
-	
+
 	// If we previously were in an area with force-played ambiance, stop it.
 	if((L in forced_ambiance_list) && initial)
 		L << sound(null, channel = CHANNEL_AMBIENCE_FORCED)

code/game/sound.dm

@@ -4,6 +4,9 @@
 		return
 
 	var/turf/turf_source = get_turf(source)
+	if(!turf_source)
+		return
+	var/area/area_source = turf_source.loc
 
 	//allocate a channel if necessary now so its the same for everyone
 	channel = channel || open_sound_channel()
@@ -19,6 +22,11 @@
 		if(!M || !M.client)
 			continue
 		var/turf/T = get_turf(M)
+		if(!T)
+			continue
+		var/area/A = T.loc
+		if((A.soundproofed || area_source.soundproofed) && (A != area_source))
+			continue
 		var/distance = get_dist(T, turf_source)
 
 		if(distance <= maxdistance)