Why does my car make a foghorn-like sound from the left rear when I go 37 mph or 55 mph??

Question

The dealer said it was the new tires, and that 17'' wheels have thinner tires, so you get more road noise.
I thought it might be in the back right wheel, or maybe the roof rack. It's a low hoooot, not an awful noise, but it's like when you blow on a bottle at the right angle and get a deep tone.
And about the speed, when i go above or below those 2 speeds the noise fades away.
Got any clues?
BTW the car is in great condition, runs great, and I just bought it used (certified, still under warranty), and I'm taking it in this weekend, but I want to be informed when I go in.
It has a turbo engine. Could that be the noise?
It's not very loud, like if I'm blasting music I don't hear it, but I have to get it fixed or it will bug me. I hate little noises.

Answer 1

Sounds like your wheel bearings are in need of replacement

Answer 2

Roof racks are notorious for making wind noises, and if some of the hollow pieces hit the wind right, can probably make the noise you're describing. You may have an end cap off one of them. The tires could be a culprit- do they have aggressive tread?
Do you have a tow bar? It has a big square hole in it, if it's open in the front underneath, it could be making noise. There are a lot of different things it could be, obviously. I'd go over the vehicle carefully, and look for anything that is either protruding, or has a cavity, that might make wind noise and amplify it. Look under the vehicle as well.
Is one of your rear windows down just a HAIR? That can cause noises, and you can't tell the window is actually down. Try rolling them all up tight. Do you have a hatchback? Is some of the rubber missing off the gasket? Wind can get around doors or rear hatch if a chunk is missing.
So, check it all out, visually, then move back to the wheels. Good luck!

The Gremlin Guy

Answer 3

I have known several cars and trucks that do this, and all had tires that were either snow tires or off road tires of some sort.

Deep grooves, particularly near perpendicular to the tire direction that make good traction on bad surfaces also make noisy sounds on normal pavement.

I have known turbo charges to make that sound as well but only on really extreme cars where the Turbocharger and scoop stood up above the hood. In that case it was pretty obvious.