I recently got a 2001 volvo s40 turbo, and after a few days of owning it I noticed the exhaust had progressively gotten louder. I found that the flex pipe needed to be replaced, and got that fixed. the car came back very quiet, more than before, but I started to here some sort of whine or whistle from under the hood, and it would change pitch as I messed with the gas pedal. I've never owned a car with a turbo charged engine, and was afraid that maybe the turbo was blown or damaged. Do turbos on these cars make a little bit of noise? it's more noticable when I turn all of the other stuff off (radio, air conditioning, ex) but once I get over 20-30 mph I can't really hear it. I haven't tested it on the highway or anything, but I did do a quick 0-60 on a quiet road and I couldn't hear anything once I got over 15mph. It kind of sounds like a far away ambulance to me, because I drive around 30mph so I accelerate up and let off, so the pitch goes up and down. I'm not sure if it's audable outside of the car. Is this a sign of a turbo breaking down, or is this what they call a turbo "spooling" and just a normal sound from under the hood?

I would appriciate any help I could get, I'd really like figure out if this is a problem or if I'm just paranoid and I'm ok.

 

Yes turbo's will make some noise.