Weird whistle/squeaking noise

[Matto]

My girlfriend has a MK6 Golf which has started making a weird noise. Its like an electrical whistle/squeal coming from the alternator area. I am yet to pin point it exactly. The even stranger thing is, it does this parked up, with the engine off, ignition off, doors locked etc. Anyone have any ideas or come across this before? VCDS scan is clear. Here is a short video of the noise:

[doylebros]

Anti shudder valve

http://www.darksidedevelopments.co.uk/products/vw-audi-1-9-2-0-anti-shudder-valve-asv-038-128-063-m.html

Common but doesn't mean anything - removal of key 20 seconds later no noise.

[Matto]

I'm don't think this is the ASV. Not even sure it has one. This is the very basic 1.4 engine. No turbo/supercharger. I am familiar with the noise the ASV makes when you shut off the engine. This is making this noise a good while after the engine has been off, doors are locked and you've been in the house half an hour.