Rear of car sounds like Helicopter?

My rear tires sound like a helicopter, not an exaust issue, the sound speeds up when I accelerate?

Sounds like flat spots. Did you recently lock up the rear wheels during hard braking or spin out? Either will put flats spots on the tread.

Is there a vibration associated with the noise? If so, there may be a tire separation.

Let me add: If the tires are old you MAY have a tire separation in a sidewall and have a bulge in the rubber hitting something as the tire turns in the wheel well.

What kind of car? A ‘whomp whomp whomp’ sound from the rear can also be a wheel bearing. Wheel bearing sounds will change as they warm up. Tire flat spots will sound pretty much the same through the whole drive.

You can try rotating the tires, front-to-back, to see if the noise changes position. If so, suspect one of the tires.

If it is a rear drive car check rearend

what kind of vehicle? (he asked kindly).

for all i know it is a helicopter (in that case its normal)