Guest
Could be loose pipes, loose or insufficient pipe saddles, vibating components within a control or isolating valve.
Check the piping system and valves as far as access permits and install additional pipe saddles where necessary.
Should the pipes be flapping around in a wall cavity, a low pressure foam injected into the wall cavity through a pin hole in the wall cladding may solve the problem.
A scan of the wall may be necessary to locate the position of the pipes so that the foam injection is correctly placed.
Good luck.
