Whistling normal?
 

Hello,

I purchased a 2015 XC60 with 40000 miles on the clock a couple of months ago and have noticed a whistling noise at high revs just before changing gear when it then sounds like a dump valve. I have only noticed it when driving with the windows down over the past couple of days so I'm unsure if it has always done it or if it's something new.
I have never owned a Volvo before, is this a normal noise or should I be concerned?
I purchased car from an independent garage but have since had the cam belt replaced at a Volvo dealership where they carried out the usual service checks and nothing was flagged up.
Any help would be much appreciated,
Thanks