Found this old thread regarding an older Humax, but the poster describes my noise exactly…
http://forums.digitalspy.co.uk/showthread.php?t=512998
A whistling/whine from I believe the hard-disk – I think this MUST be a clear faulty unit. Its not LOUD but it’s SOLID and NOTICABLE and the sort of piercing whistle that as you turn your head through 180 degrees comes and goes at reproducable points of compass.
Although I’m pretty sure a lot of older folks wouldn’t hear a thing. Such a subjective thing is noise.