wierd resonant noise

Dear all

I have a new Octavia 2.0 TD DSG, bought in May.

It's fine in all ways, except that it makes a strange resonant burbling or howling noise at almost all speeds (i.e. anything between 10 mph and motorway speeds). It's not road-speed related, it's not wind noise, and it doesn't sound to me like road noise (it's most audible on smooth surfaces, when tyre noise is least present). It's been there pretty much since I took delivery. It seems to become audible, or more clearly audible, after the car has been running for a mile or two, and is at least partly warmed up. Particularly evident on a light throttle or the over-run. I'm not sure whether or not it's engine-speed related -- with the gearbox in auto mode the engine speed doesn't vary much in any case. Could it be an exhaust noise (if so, I'd be pretty sure it's not meant to be there)? A 'feature' of the DSG box, or some DSG boxes?

Has anybody come across this? I've twice had the dealer's people listen to it, but they claim the car is making no noise they wouldn't expect. In which case they must be used to selling and driving some very odd-sounding Skodas.

Has anybody got any ideas? It's driving me nuts.

Thanks!

dr cox