While trying to get an acoustic recording of my Predator 212 engine, I noticed that if the recorder got too close, there would be a clicking sound, which I almost immediately figured out was the magneto. Once again, I wanted to know what it would sound like with a pickup coil, so I finally got around to recording it along with some acoustic recording. The engine is at idle for most of the recording, but I give it a couple of revs and kill the engine at the very end, sadly without the pickup coil.
The sound of slow revs almost sounds like I just increased the sampling rate of the audio or something, but I promise that was recorded in real time. The only modification I did to the recording was to make the coil part of mono instead of being on the left channel.
I got bored one day, so I started listening to things around my room with an electromagnetic pickup coil, commonly used to record telephone conversations. My ceiling fan and the lights on the fan are connected to two different switches, which have both been replaced with smart switches from TP Link. The lights are on a smart dimmer which uses a triac to control the brightness of the lights. I just thought it was cool how you could hear the change from the prospective of the triac.
In a dorm I was at, I discovered that there was a buzzing noise coming from the dryer. Upon closer listening, I discovered that it was the synchronous motor powering the timer. Basically, a synchronous motor is one that is synchronized to the AC frequency it receives, which here in the states is 60hz, so 60 rotations a second or 3600rpm. All you have to do to turn that into a timer is gear it down and you've got a accurate enough timer.
I think something might have been wrong with the gears in that timer. I have listened to other dryers like it and they don't have the same sound.
A couple months ago, I took a Toshiba 250gb laptop hard drive from 2009 out of its misery after it lost its data connector. After removing the head assembly, I was left with a platter, which I proceeded to remove. It turns out that if you put your finger to the motor and allow it to spin just a little, the load is too high for the motor to pass the slow spin, and the result is quite musical, creating a note-by-note e minor chord, if that is even a thing.
Over the years of messing around with dead hard drives, I have acquired my fair share of recordings of launching platters and motor controllers freaking out. I might upload those some day, but for now, enjoy this little recording.