What’s this strange whistling noise?

Ever since I got the front mirrors of my Kia Sportage 2012 replaced, there’s been a whistling noise coming from the driver’s side of the car. The sound starts once I hit about 40mph. It stops when I roll my window down, so it makes me think it’s not the mirror, but possibly the window itself. I can’t figure out exactly where it’s coming from. Any idea what it could be?