High-Pitched Whine

Has anyone else noticed an extremely high-pitched whine from the RCT715 when it's switched on? It's right on the edge of my hearing range, so it's more like a sensation at the back of my head, but it's definitely coming from the unit is it corresponds with it being turned on and off. Not really an issue as I don't think I'd hear it when cycling, but I'm just hoping mine isn't about to fry itself.

EDIT: just tested and it seems to be at approximately 8000Hz and 16000Hz. Seriously hoping all the dogs in the neighbourhood aren't going to be chasing me!