I’ve started to notice a noise when accelerating at low speed. 
It’s not apparent when cruising, or decelerating or sitting and revving the engine.

It sounds like blowing over an open bottle, a constant “woo” noise.

Both my front wheel bearings have been replaced. My water pump and timing belt were replaced. My aircon fan has been replaced.
I’ve had a look for leaks on the intake piping, there is nothing obvious. 
I thought it might be the turbo echoing around the cavity where the aircon intake and wiper motors are located.

The sound is more noticeable when the engine is warm. 
If I accelate hard the sound does not get louder, but it’s still there.
Is it a noise every mkii has and I shouldn’t worry? 

 

It’s a 170 4x4 tdi

 

turn air con off and on to see if there is a link.

Tyre condition ok ?  Superbs like to chew up rear tyres which can cause sawtoothing and tyre noise (although it may be variable at different speeds...)....worth checking, especially the inner edges.

 

Nah, the tyres are virtually new. And the noise is there from about 10kph

No difference with ac on or off. 

Replaced the air filter today. Seems to have done the trick. I feel like an idiot 

The car had 60000km service 3000km before I bought it, around 12months ago. Just after the Australian bushfires. I presumed they replaced it at the time, given Sydney had some of the worst pollution in the world over that time. Wasn't until I bought the new one that realised how bad the old was. There is no chance it had been replaced. I had assumed it was some fandangled fancy Skoda filter. 

F##k Skoda dealer mechanics!!!!!!! My car is never going to a dealer mechanic.