Tapping sound from the rear

Hey guys ,
2015 Prius V 50,000 miles and circulating kind of noise coming from driver's side , rear wheel...
I can hear it more at lower speed but only due to the bigger noise inside at higher speed. It is circulating , tapping sound that slows down when car slows down and speeds up when car accelerates. It is kind of sound like something attached to the tire and is circulating with it. I checked tires, had a nail but they fixed it and rotated tires. Thought problem fixed but ... no , sound still there. Wheel bearing? But at 50,000...? I have a feeling I feel it on my foot , that tapping but maybe it's just my imagination. Couple friends drove to check and they hear and feel same. One solution is to keep the music loud but..
Any suggestion? Thanks.

 

Thanks. So you think there may be disc scrubbing at one spot on the pads and that's why it is cyclical... I thought about that too. Will check.

 

No change and repaired tire is now in front, passenger side...

 

Guess what last year it turned out the wheel bearing in the left rear needed replacement. This month July 2018 and 21k later the sound came back to the rear. Exactly same and not sure if another wheel bearing on the right now needs to be replaced or new one failed. Just recently visited tire shop to rotate and balance tires and the had to replace one tire on the rear right due to side bump. Now new tire is in front left but they said it happens from driving into pothole. Maybe the right wheel bearing got damaged too during same condition? Anybody with similar problem. 15 Prius v with 71000 miles ....
Also on rear new (replaced same time last year at 50k) rotors I can see a lot of lines. Front are smooth. So weird. Used centric rotors and and centric ceramic pads.