I am having the toughest time figuring out what's wrong with my car. Whenever I go above 30 mph I hear a noise coming from the back of my car that sounds like a helicopter. I have gotten new rear wheel bearings installed, As well as new brake drums & shoes. I do not know what the problem could be. I would like to add that I started to hear this noise after getting new tires put on my car about a year ago. To troubleshoot the tires I went in for a tire rotation. Even after the rotation I still hear the helicopter noise coming from the back of my car. If I only roll down the front windows I hear nothing, but when I roll down only the back windows that is when I hear the noise. My question is what do you think it could be? I also would like to say it has crossed my mind that maybe they didn't rotate my tires so I am going to try to have them rotated again and this time I'm going to mark my back tires with some type of chalk to see if they're doing the rotation. 2014 Nissan Sentra Sv, 137,000 miles. New tires. New rear wheel bearings(both sides). New brake drums & shoes(both sides) Good condition tires. No car wrecks. I sat there with the mechanic for the installation of the bearings, drum, & shoes.