I remember waterbeds were bad about it(30 something years ago) if you were all fucked up, or that's where I first heard it, but I still hear it quite often so who knows. We're not crazy, just a little unwell.

Microwave hearing (Frey Effect) can occur without metal implants. Many are now experiencing this and other health effects known to be caused by microwaves at 3AM which is a time many smart meters are set for large transmissions.