This sort of thing always reminds me of Christmas Vacation's Grandma saying "it's making a funny squeaking sound". So we're all at my brother- in-laws and he has a Mac mini connected to a pioneer avr, amongst other connections like blu ray and wii. Only when feeding from the mini does he get a high pitched whine, both with streaming and disc play. Not a 60hz noise, but much higher. He does not have cable TV and all electrical connections run thru a 2-prong plug, so no ground-loop issue.

Any thoughts?

What output is he using on the mini? And what generation of mini is it?

HDMI from mini to avr. About this mac says mid 2010, 2.4ghz IC2Duo, running OSX Lion.

While looking at connections, he does have a cable modem, but he's using the Ethernet connection from modem to mini...

Hmm. So not so easy to just plug in a pair of headphones and see if you hear it... might be worth a go anyway. Just see if it's a software thing or a hardware thing.

You will need to buy a white, proprietary Apple de-squeaker. They are a bit pricey, but your life will be better with it of course and you will never know what you did without it. There will be a newer de-squeaker out next year that won't be much better, but you will be convinced through clever marketing that you need it. You seem smart enough to know that is just a rouse since you already own a 2 year old Mac...

Sorry, I couldn't resist.

Smart, of course but also very gullible. Search for de-squeaker turned up nada. A link, perhaps?

I've heard that type of noise before, but it was always the analog sound card picking up something from within the computer. HDMI should be digital all the way, so noise shouldn't be able to sneak in.

In other words...I dunno.

I actually own a de-squeaker...

This picture is almost a year old, but she is still compact and really has a knack for ripping the squeakers out of her toys....

very nice photo of your dog (He speaks). :-)