Screeching noise from PSU, not fan. Need Help

I have a Tt 875W PSU which has been used for 2 years. A few days ago I just moved home and since then the PSU keeps give me loud noise which even gives me a bit headache and cannot use the computer anymore. The noise sounds like if there was a thin cord gently touch a fan.
After some testing I found the problem is rather wierd.
The noise becomes louder as the power output goes higher. The way I tested is to turn off the PSU with the switch on it, then turn on, finally turn on the computer. The noise keeps increase, and still exists even the PSU is powered off with connection to external power socket. And I can still hear very low but same kind of noise come from it when it's switched off but is connected to external power supply (socket on the wall), of course the fan is completely stopped at the time.
I think this cannot be casued by dust, as the case has pretty good dust prevention and I cannot see significant dirts inside the PSU.

I have no idea which part is faulty, and I need some advice about whether or not send this PSU to RMA, since it's still in warranty period.

Thanks for the help.

I am not sure about your sound description.

It could be something has moved or come loose when it was moved or it could be a failing component. If it is under warranty you should look at sending it back.