A4 high pitch noise on acceleration

[bob smith]

I have a Nov 2000 A4 1.8 - 57k on the clock. Recently I have noticed that whenever I press the throttle I get a high pitch noise for a few moments - it then goes away and is fine until I press the throttle again. There is no noise on breaking or that I notice when starting the car or during driving post-acceleration (e.g. maintaining a steady speed). Any thoughts and guidance much appreciated.

[Dozz]

Does it do it if you rev the engine in neutral and not moving. Does it sound more like a whistle? Sorry but noises are hard to pin point even if you get to here them yourself

[bob smith]

There is no noise just revving the engine in neutral - starting to think it is something to do with the wheel area. Sound is like a short two tone high pitch screech lasting moments only. I'll take it to be checked out may be a simple brake pad problem or something

[evilscotsman]

belt slippage under load? or a vacuum leak?