Pinging - I've never seen an electric hot water heating element that, after a period of time, did NOT ping. It is due to scaling on the element building up, and when the element energizes, differential expansion of the scaled element results if this 'pinging". As for the "squealing" - Appears to not be a water heater originated sound (squeal happens both hot and cold). Most (all?) hot water heaters do not have integral check valves. Suburban further recommends a check valve not be installed immediately at intake of heater. There is however, a check valve at the city water intake hose connection. Check valves can squeal at initiation of flow through them. To test, I'd disconnect city water, turn on unit water pump, then open faucets - if no squeal, noise is likely from the city water inlet check valve. Changing water regulator pressure pressure may remedy issue.
2011 3500HD Duramax/Allison/90 Gal Aux
2015 HD Limited Low