For some reason, the function ChatUI_HANDLE_EVENT_MESSAGE in ChatUI.js only plays the "new message" sound, if the message is not older than 2 minutes.

 

Unfortunately, the javascript function compares the message's server time to the client computers time. So in effect, the sound is not played, if the receiving users watch is ahead of the watch in the web-server.  

var time=msg.ServerTime.getTime();

if(time+120000 > new Date().getTime())

{

	ChatUI_PlaySound("type");

}