siren like noise from turob?

[dickbastardly]

Hi all
I have a Saab 9-3 Tid 1.9 2010 with 35k on the clock.

Just recently I am getting a noise I think from the turbo that sounds like there is an ambulance with it's siren on in the distance.
It kind of gets louder as I accelerate then when I take my foot of the throttle to change gear it dies down then increases as I accelerate again.
It's louder when the car cold.

I have just had it serviced and I don't think the noise was there before the service.
Any ideas what it could be???

Cheers
Andy