Loud noise high speeds in top gear Ford Focus Cc

[Alexpingu]

I’ve noticed a new unusual noise when I’m doing speeds of 50mph plus, it’s like I need to change gear even though I’m in 6th gear. Sounds like a sesna plane.  It passed its mot 4 months ago, I took it into a jail fit garage today where it had its mot they didn’t bother test driving it they just got it on the ramp and said that wheel bearings are ok but the back two there is a slight noise coming from them but they can only spin it so much on the ramp. I was told to keep an eye on it but it’s safe to drive. I have filmed the sound below, Any advice please.  Thank you Link to video