I only have the car for 5 months now, with 48k miles and it drives very well but only lately, I hear a soft high pitch whine coming from the engine inside the car when it is idling.

I never noticed this before because I have been using the A/C.

I due hear the slight growl of the engine from the muffler, too.

The high pitch whine is still prevalent even when I have the fan turned off that just blows in fresh air through the vents. In other words, all switches are off.

Has anyone else noticed this sound? Is it related to the turbo being active as well? Or is the sound normal?

I have no performance problems.

 

I washed my cars engine bay when I got my car and the whine came up. My issue was the alternator something is in there that will cause a whine and you can hear it through out the rpm range. It's still functioned properly no codes or lights illuminated just a loud noise. My car had 65000 miles on it when it happened. I found the issue using a hose to my ear and also a metal stethoscope that I used to probe around. It was surely louder at the alternator.
Hers the bad news! If it is the alternator the thing cost me 450.00. I was able to get the mechanics discount at my dealer because of my experience and relationship with them. Do not I repeat do not buy any aftermarket alternator it will not work and will throw a voltage code on your dash. I tried this and learned the hard way. You can read some posts on here about the same issue of reman alternators. Volvo is very specific on voltage control!
Good news is I got to where I could change the alt in about 30 min. First one took me 4 hours.