Here, I conneced a solar panel (via a transformer) to a sound interface as if it’s a microphone, to reveal the subtle pulsing and filckering of various light sources. If you don’t like 50 Hz, this video isn’t for you.
Thankfully, the infrared light from my camcorder is apparently very clean (not pulsing), so I can use that to see things in the dark without affecting the sound.
The transformer is just designed to convert 230V AC to 12V DC, so its audio properties are not very good (it muffles things a lot). Ideally, I’d be using an audio transformer that’s designed to sound good, but this is all I had available. I am using it to remove the DC current that the solar panel makes, because I don’t fancy putting 17.5V into my Quad-Capture (sound interface)’s mic input. I originally tried to make a high-pass filter to remove the DC, using a capacitor and resistor, but it only worked until the capacitor became fully-charged, at which point the sound faded. It was much clearer-sounding than the transformer, but there was also a huge amount of background noise.
I want to revisit this idea in the future, especially to take it for a drive at night, listening to the street lights and car lights (since modern cars use PWM to dim the tail lights).