Ok, I have absolutely zero experience with turbos, thus I need the assistance of more experienced members. I took a 2001 2.4L V70XC turbo out for a test drive the other day, when the turbo was spinning up it sounds like a siren once you let off the gas it stops. First time it happened I actually looked up to see if a cop was coming up from behind. Is this to be expected, or is the turbo on it's way out? The rest of the car was in fine shape, the only thing I am unsure of is the turbo.

 

Obviously the type of sound and the volume is a really tough thing to define in type. The best thing you can do is drive several similar cars and if one is significantly louder than another then it would be suspect. Based on several other threads you have posted here it appears obvious that you should not be relying on advise from internet forums to determine whether or not a 12 year old car is a good candidate for a trouble free used car. You should be using a qualified independent mechanic who is thoroughly familiar with Volvo's. It may be the best $100 you have ever spent.

Edit:

Just noticed and replied to the thread you started about having changed the fuel filter on an S60T, so how do you not know what a turbo is supposed to sound like?