> “It’s simply the electromagnetic fields in your own body, what we refer to as capacitance, affecting the circuitry through the electromagnetic field surroundi

> “It’s simply the electromagnetic fields in your own body, what we refer to as capacitance, affecting the circuitry through the electromagnetic field surrounding some device,” says Albert Glinsky, ... This 'explanation' makes the instrument appear even more magical. It's less mysterious to describe it in terms of a resonant LC oscillator, where C (capacitor) value, i.e. its capacitance, is affected by the presence of hands or other conductors between the theremin plates/antennas. A sidenote, in common implementations the C change is later translated into L value, i.e inductance, change. More details [0] Speaking of the mentioned clever espionage device. In modern days the similar principle is applied but using lasers and room's windows for vibrating surface. However, the thicker glass used in contemporary thermal packs may dampen the acoustic vibrations; still, by itself it's an acoustic resonator and the question is how sophisticated is the receiver. [0] https://electronics.stackexchange.com/questions/11573/how-does-a-theremin-antenna-work https://electronics.stackexchange.com/questions/11573/how-do...