Upon arrival system not on, turned up temperature so that heat pump system would run. After a few minutes of running the noise started. Checked zoning and air handler in attic and everything working properly with that. Checked outdoor heat pump and found that the refrigerant pressures were higher than specifications. Pressures were getting close to 500 psi on head pressure. Adjusted refrigerant levels to proper operating pressures and noise went away. System must’ve been going into high pressure lockout and restarting itself over and over. Advised customer to keep listening for noise to see if we need to further diagnose.