The sound seems rhythmic with chain link movement. Is the chain properly routed through the cage? is the chain riding up onto the tops of the tension pulley's teeth (being held from derailling by the cage sides)? Is the B screw and gap set so the guide pulley isn't touching the cog teeth and/or trapping the chain between the pulley and cog teeth? Does the guide pulley have the OEM amount of end play or has it begun to be able to have a rocking type of slop?

Sure sounds like a chain rub or chain/teeth meshing sound. I have to assume the shop didn't install the chain and cassette wrong, they reset the der's adjustments with each change of a part. Did they test ride the bike enough to confirm the noise before doing any service? Andy