The fixture, timing, and kind of sound are more informative than the word “banging.”
The short answer
Note which valve, appliance, or fixture starts and stops before the sound. Record whether it is a single thump, repeated vibration, whistle, ticking, or movement. Do not alter pressure controls or secure concealed piping as a guess. Ask for inspection and measurement when the symptom is recurring or severe.
What to notice
Make a short sound log
Write down the time, active fixtures, hot or cold side, floor, and whether another appliance was filling. A washing-machine valve closing quickly provides different context from ticking as hot piping warms. An audio recording can preserve the sound, but it may not capture where it originates or how strong movement is.
Look for accompanying changes
Add low or high flow, valve stiffness, pressure measurement, leaks, or new fixture work to the record. A sound alone does not prove excessive pressure, a missing arrestor, loose piping, or equipment failure. The provider should connect the proposal to the observed system and relevant measurements.
Ask what the repair is meant to change
A recommendation might involve a fixture valve, appliance control, support, pressure-control component, or another condition. Request the target symptom and test for success. If opening a finish is proposed, ask what evidence identifies that location and who restores the surface afterward.
One useful question
Can water hammer damage plumbing?
Pressure transients and pipe movement can be important, but this site cannot assess severity from a description. Arrange evaluation when noise is forceful, new, or accompanied by leaks or fixture problems. Ask the provider to document measurements and the basis for the proposed correction.