Recently my 2003 Fiesta LX (KG03 ZTU), has been making weird sounds in the back. First it was a strange humming sound which seemed to stop completely when I press on the brakes and start when i release. 

Now the sound is alot louder and seems to be relative to the speed of the car. you can hear in the video the alternating sound which sounds like something grinding/rubbing (driver side only). It is sounds louder when turning sometimes and when going over a speed bump it occasionally stops completely, then returns a few mins later..  

Is this the bearing or something else?

video: https://imgur.com/a/doMTjCT

Thanks

If applying the brakes makes the sound change, it's probably the brakes.  A wheel-bearing sound will continue even if the brakes are applied.

Do you have drum brakes in the back?  If so, it's possible the shoe liner has fallen apart.

6 minutes ago, orangecurry said:

If applying the brakes makes the sound change, it's probably the brakes.  A wheel-bearing sound will continue even if the brakes are applie

when I first heard weird sounds it stopped when brakes applied but a week later this new sound happens but this one doesn’t stop when I press the brakes.. not sure if they are related though.

Take the rear wheel off.  Look at the rear spring.  If it is not broken, and all looks normal ,if you have proper stands... take off the drum.  What is happening inside.