Inductors Pt.1

For the past few months I've been experimenting with building and using Inductors as audio pickups.  An inductor is essentially a coil of wire, and when used as an input on a sound recorder, it picks up any EM waves nearby.  You can use it to listen to your computers clock speed, the buzz of mains power, or do some really interesting things with magnets like what I've done.

I've been calling this a sort of "contact-less contact mic" because the coil pickup is physically detached from the surface.  Without going to deep into the physics of magnets (because I'm terrible at explaining it) the magnet induces a static magnetic field, the nearby coil picks up the static field.  When the magnet vibrates, the coil creates an alternating current (AC) which the audio recorder turns into digital audio.  This means that I can attach a magnet to any surface (ferrous or otherwise), and the coil will pickup the vibrations from the magnet.

Here's an example:

I streched a 70 foot steel wire across my backyard last winter break, and recorded bowing it and malleting it.

This was my setup:

My homemade inductor is plugged into my H4n field recorder, and the coil is placed near (but not touching) the magnet.

It produced some really cool bowed gong sounds:

Inductor - Fish Wire Part 2 by Krevuk

Since then I've created a newer coil, out of an old solenoid, this coil is significantly bigger, which introduces some different sound characteristics.  I'm looking into creating a nice enclosure for it, with a build-in preamp, and balanced XLR output (an inductor coil is essentially a dynamic mic, without the diaphragm or magnet).

I've also tried flipping the signal flow and using it as a speaker.  I plugged the inductor into a output jack, and placed a magnet near the coil.  The inductor produces an alternating electromagnetic field, and the nearby magnet vibrates to the field.