How do I keep an audio file active only within a specific area?

Well for this, there are multiple ways,

• One way is to make the sound play within a brick that's within the room.

• Another way is you could insert a sound into the playergui and play depending on whatever brick they're touching.

Now the first one is pretty self explanatory but I should explain the second one.

Now like @Mokiros said, You could use touch events, For this we should put the sound in the player gui, so...

game.Players.PlayerAdded:connect(function(plr)
	local audio = Instance.new("Sound") 
	audio.Parent = game.Workspace[plr.Name]
end)

Now that we've set up where the audio is, We can now change it with an touched event,

game.Players.PlayerAdded:connect(function(plr)
	local audio = Instance.new("Sound") 
	audio.Parent = game.Workspace[plr.Name]
	audio.Name = "LocalAudio"
	game.Workspace.'Partname here'.Touched:connect(function()
		game.Players[plr.Name].PlayerGui.LocalAudio.SoundId = "Sound id here"
		game.Players[plr.Name].PlayerGui.LocalAudio:Play()
	end)
end)