How do certain regular objects play audio with no speakers if a radio transmission is powerful enough?

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I saw a TIL post talking about a radio station that transmitted so much power that people nearby could hear it in their furniture. How is that even possible? I though speakers were made to that audio could be correctly relayed yet a spring mattress can play audio?

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A radio signal is literally the sound wave, but “riding” a carrier wave. Tune into that wave using a metal antenna that vibrates at the same frequency, so you are “riding” alongside it, by filtering out other frequencies, then amplify the sound, and that’s a radio. Crank the power up enough and that wave will be so powerful, the antenna itself will vibrate loud enough to hear, even if that “antenna” is a pot or a filling.

AM radio only needs a very simple circuit to “demodulate” the audio signal; a rectifier. A poor quality rectifier circuit can sometimes be created quite by accident, such as by having two dissimilar metals in contact, or a metal and a conductive solution. Metal fillings and saliva can do it!

If the radio signal is very strong, it can overcome the lousy efficiency of such a circuit and make things vibrate just like a speaker would.

I was wearing a large belt buckle and someone asked me if I got good reception. Lol. No, but I guess it’s possible.

At its most basic, a receiver circuit, consists of only three elements: an antenna, which picks up an electromagnetic radio signal; a detector, which is an electrical component that converts the radio wave to an audio signal the human ear can pick up; and a transducer, which is anything that acts like a speaker.

In extremely rare case, things not a are not actual receivers can accidentally act like a receiver. If you have something electrically conductive to act as an antenna, something to act as a semiconductor to detect the audio signal, and something to vibrate enough to produce noise, you’ve got a very primitive accidental receiver that can turn radio waves into sound.