What I really want is something that detects any EMF above 60Hz.
When I was a kid I used to hook a coil of wire and a diode to a piezo earphone. I then listened to the emissions of various devices in my house. My Amiga 500 was particularly interesting.
I ran across a few projects that do the same thing but add an opamp and recording so you can generate sounds for electronic music.
Can you give more detail so I can do this with my kid? I'm a not a hardware person but handy enough I think. How would I connect the diode to the coil? By coil do you just mean wound-up wire or is this an electronics component?
Anything above 0Hz radiates. EMF is short for 'electromagnetic field' which even DC produces, so I guess I could have worded it better.
In any case, I would want to detect the emissions from the CPU, memory bus and SD card traffic. Not all cameras are WiFi. Sure, that won't detect passive listening devices or other advanced techniques, but most people now are worried about video and that will have certain characteristic emissions.
In most cases it's a collection of different sounds including clicking and humming. In the case of my GPU it's a high pitched whine (inductor noise). You can create music by running specific instructions.
When I was a kid I used to hook a coil of wire and a diode to a piezo earphone. I then listened to the emissions of various devices in my house. My Amiga 500 was particularly interesting.
I ran across a few projects that do the same thing but add an opamp and recording so you can generate sounds for electronic music.