microphone to record electromagnetic field of headphones

[timdevine]

Hey all,

I want to record the electromagnetic field of headphones from a distance. I figure something like a guitar pickup would work? Are there any such microphones?

Any thoughts?

 

[DF96]

A microphone picks up sound, and turns it into electricity. You want to pick up EM (presumably the magnetic field?) so you want an inductor. Try a 5mH RF choke?

 

[cbdb]

Eaves dropping? The field will be very small at a "distance" (more than a meter or 2). Just tried my medium sized over the ears headphones on loud right next to my bass guitar pickups (an inductor). With my small amp turned up full I could just hear the music (nothing below 1khz). 3 inches away, I couldnt hear anything. So its possible but not easy.