This is probably nothing to do with it but I'll mention it anyway.
When I first powered up my system, 4 x AM882 and CNC4YOU Nema23 4Nm motors, it sounded like a load of whales singing from one particular driver and the motor was noisy when running. I thought it was goosed so I tried another motor on it with the same result. There is a utility with the AM882's called Protune and I had been playing with this connected to one of the drivers via a special cable (connections available on Leadshine website to make one). I therefore connected the noisy driver to Protune and ran the Auto Current Tuning section, immediately no more whale song and motor nice and quite when running. Without looking at the manual for your drivers I don't know if this utility is relevant but it shows that something on the current side was having a huge effect on motor noise.