I have not had this problem when connected to my laptop via the TV Connector, however can see it happening as when on the computer you can do other things while listening to music/youtube, and you can then stream from another source accidentally, this I do suppose could cause this. Say the first stream had ended and you click on a window that has sound and you get the tone, then the first starts up and dings again. Not sure, but can see the possibilities.
Alternate selection procedure can be changed at your fitter. There are three choices to hook up to the TV connector. One, automatic connection whenever sound is available without any dings or touch of button, second, what you and I have, which gives a ding and a short push of either connects, also can disconnect with a long push of the high side, then re-connect with another long push of the high side through whatever programs you have, and third, no ding, connect with a long push of the high side, disconnect with a long push to the high side, and re-connect by another long push high side. Realize that if you have more than the automatic program you will have to cycle through them to re-connect.
RDB