I had my bike on a stand yesterday and decided to check the rear wheel for any issues. I then noticed this squeaking noise coming from the rear hub. It happens regardless of whether I am pedalling or not, and the intensity varies with speed.
A video of it can be found here:
What could be the causes of this noise and is this something that needs to be looked at by a bike shop?
In my experience, that sound is caused, not by the hub, but because the tire is rubbing against the brake pads. This can happen if the tire is slightly out of alignment or isn't properly trued, or if the brakes got accidentally bumped while riding (depending on your type of brakes). Try spinning your tire and watching it move between the brake pads, and you should see some wobble to it.
If this is the case, try removing the wheel and putting it back on (spin it again before tightening it in, and adjust it accordingly). If that doesn't do enough, try adjusting the brake pads (a different procedure depending on what type of brakes you have, so I can't really elaborate). If it's still giving you trouble, then the wheel is misshapen, and needs to be re-trued, which is probably best done by a bike shop, but isn't too hard to figure out on your own.
