2008 Prius Noise follows speed

have you checked your tires? Make sure they are not worn and bumpy?

 

Noises that get louder with speed are usually associated with bad bearings and tires. If it's a bearing, the noises can change as you turn the steering wheel.

The tires should be inspected with the car raised off the ground. Then take a good look, even slight uneven wearing on the tire will make a tire noisy when you're at speed.

 

Some tires get much louder with age.
Loud enough that you might think it is a bearing issue.

Do you have anyone else you can swap tires/rims with as a test?

 

You may also want to try swapping the front and rear tires, then see if the suspect noise changes location.

When jacking up the front wheels, check for bearing wobble or movement by holding the outer edge of the tire at 9 and 3 o'clock, then push/pull on opposite sides, creating a shaking motion. There should be no play in the bearing when doing this, short of the front wheels trying to turn left or right, which is why you would also verify this again at 12 and 6 on the wheel.

How many miles ago were the bearings done?

Did you replace the two (2) front bearings with OEM, or something else?

 

I just had a New aftermarket bearing fail within a month of being installed. Very strange.
Got a replacement since it was under warranty, but still very annoying

 

Looking back through the archives ... "distant Cessna" was what one of my wheel bearings sounded like in my old Gen 1.

That one was a puzzler ... none of the ways worked that people normally recommend for figuring out which bearing it is. Attaching a ChassisEar at all four bearings and going for a drive picked out the failing one in seconds flat, though.