Every now and then I hear someone retell the old story of someone hearing a familiar tune “in their head” and realizing it is coming from their mouth—after receiving a new dental filling.
The MythBusters TV show claimed to have debunked it but I’ve seen various discussions claiming to debunk their debunking. Yes, dissimilar metals can create a diode-junction but even after we put aside amplification, antenna, and related issues, isn’t superheterodyning the fatal element? That is, hasn’t all commercial AM radio broadcasting for nearly the past century used superheterodyning?
It seems to me that without a superhet circuit tied to that dental filling, it would be impossible for the humanly-audible hearing-frequency-range music or news broadcast to be “extracted” and heard.
I would not rule it out. Old fashioned crystal radios did work.
The superhet function is just for sorting out and selecting a particular channel. But if you are close enough to a strong transmitter, you might get a strong enough signal without.
Never did. But I will say that as an old ham radio nerd and fiddler-about with electronics, I find the idea of fillings picking up radio stations plausible. It’s the sort of weird thing that’s liable to happen especially when the field strength is really high (e.g., you’re nearby a transmitter). Even without any funky crystalline or diode effects, just plain capacitance can do it. An old prank which I always wanted to try was the “talking newspaper” – two sheets of foil in a newspaper, separated by a page, with a powerful audio signal fed to them. It’s like a primitive electrostatic speaker.
I don’t know what Mythbusters might have done on this, but it’s a hard one to bust because it’s fair to say that the vast, vast majority of tooth fillings do NOT pick up radio stations. You’d want to figure out the range of plausible mechanisms and try them each out, and even then you’d only succeed in ruling out those scenarios you tried, not in showing the impossibility of the thing.