I was curious about the theory that vibration applied to wires and/or electronics would generate some kind of signal.
Try this. Get a male XLR connector, and solder a 50-100 ohm resistor between pins 2 and 3, and connect pin 1 to the XLR shell - this emulates the source impedance of a microphone. Connect this through a typical cheap guitar-store microphone cable to any reasonably low-noise, high-gain mic preamp, and crank it up to full gain and listen.
Now slap the microphone cable around, and you will hear the effects of cable microphonics - they're obvious. Substitute a typical pro-grade cable (i.e. Belden 8412), and you will hear a significant difference. You might actually be able to repeat this with your phono-cable leads - it's just that the cartridge itself is microphonic as well, so it's less definitive.
But that's of course NOT the reason that some fuses have sand in them. The sand keeps the fuse filament from failing for mechanical reasons (i.e. shock, mounting position) when the fuse is operated continuously near its rated current, and the filament softens.