The part(s) or condition(s) listed below for the symptom Water Heater making noise are ordered from most likely to least likely to occur. Check or test each item, starting with the items at the top of the page.
When the water going through a valve is restriced it will often produce a whistling or squealing noise. Confirm the in-coming cold-water valve is fully open.
If the burner is hissing and popping for a couple of minutes when it first ignites there may be condensation dripping onto the burner. If the noise persists, the tank is likely leaking and dripping water onto the burner. Look under and around the bottom of the tank for leaks. If the tank is leaking it will need to be replaced.
Electric waters heaters depend on heating elements to warm the water in the tank. If an element is covered in sediment, it will make a hissing noise. You can try uninstalling the heating elements and cleaning them but if one or both of the elements are corroded, they should be replaced with new ones.
Over time mineral deposits and sediment from corroding anode rods can buildup in the tank. When the tank is heated, air bubbles can form under the sediment and then release causing a popping or rumbling noise. The water heater should be flushed out once a year to help keep the sediment from building up. If flushing the tank doesn't stop the noise the water heater will likely need to be replaced.