Hi everyone,
I will take the liberty of commenting on the problem since a while ago the same problem came up in my site. The issue has to do with the filters and the application navigation system. When you get the echo you can stop it If you push pause in the application play-pause botton (in the ispring application I mean). This is caused becasue both the filter and the application Ispring swf file are playing the audio. One is a few seconds behind because it takes longer to load and start.
The solution:
Either set the ispring to standard theme or
Change the navigation format to none in the quiz port
Hope it helps.