Where does Messages.app store its "Play sound effects" setting? I'm trying to write a script to configure the system and various apps to my liking, mostly via defaults write. I got stuck with Messages' Play sound effects setting (under General). I think this setting might be new in Mavericks.

I couldn't find it in any of the *iChat*.plist files under ~/Library/Preferences, so I watched the whole directory for changes with FS events, and it doesn't seem like that setting is affecting any of the files in that directory.

Any ideas about other locations where Messages.app could be storing this setting?
Since Messages.app is a sandboxed app, the preferences would be under ~/Library/Containers/:

~/Library/Containers/com.apple.iChat/Data/Library/Preferences/com.apple.iChat.plist


or look through ~/Library/Containers/com.apple.*iChat*/.