WowAce

Since 4.0.6, they have updated the Sound API to allow you to specify which sound channel you want to play a given sound on, so you can have addons play sounds again even if sound effects are disabled, like they used to do before patch 4.0.

http://us.battle.net/wow/en/forum/topic/2065568826

MainWindow.lua(2609): frame:HookScript("OnShow", function() PlaySound("igCharacterInfoOpen","Master") end)
MainWindow.lua(2610): frame:HookScript("OnHide", function() if frame:IsVisible() then PlaySound("igCharacterInfoClose",Master") end CloseTradeSkill() end)

Queue.lua(2543): frame:HookScript("OnShow", function() PlaySound("igCharacterInfoOpen","Master") GnomeWorks:ShowQueueList() end)
Queue.lua(2544): frame:HookScript("OnHide", function() PlaySound("igCharacterInfoClose","Master") end)

ScrollFrame.lua(776): PlaySound("UChatScrollButton","Master")
ScrollFrame.lua(785): PlaySound("UChatScrollButton","Master")

Window.lua(864): PlaySound("igMainMenuOptionCheckBoxOn","Master")