New Hot Water Heater Or Prv Valve Issue

I recently had a new gas hot water heater (apparently the dreaded flame-lock whirlpool) installed with a new thermal expansion tank.

On hot-water demand once the gas flame starts the heater makes a popping sound followed by tuning fork ringing sound. After about 10 seconds all sounds from the water heater stop. Here is a video:

The installer came and adjusted an internal pipe of the heater. The heater still makes the initial pop but the bell sound…

New Hot Water Heater Or Prv Valve Issue