I just got a cheap wireless phone charger from ebay, and noticed it making a very distinct high frequency squeaking noice. Here is how i fixed it, or made it almost inaudible. (Didn’t take any pictures, sorry)
Tldr; Basically open it and glue the coils down.
(15W Qi Fast Wireless Charger Stand 4in1 For iWatch 6/5/4/3/2/1 iPhone 11 XS XR 8)