recording EM fields intentionally

[logey]

[I originally posted this in Recording Techniques...I'm moving it to DIY because it seems more appropriate.]
I've been reading about this German artist named Christina Kubisch who does audio installations where the "viewer" roams around the installation with wireless headphones designed to pick up the sounds of electro magnetic radiation in her installation. She also maps out "Electrical Walks" in various cities that guide the listener (with a loaned pair of these special headphones) to various locations with particularly unique sounds. Its hard to explain, so check this out if it sounds interesting. http://www.cabinetmagazine.org/issues/21/kubisch.php
The linked page also has some audio examples, some of which i find very cool.

So my question is, how can I devise a "Microphone" to intentionally record these sounds? I've tried the detuned AM radio trick...works, but in addition to the radiation you also get the white noise of the detuned radio. In addition, I'd kind of like it to be directional. There must be an easy way to do this...any ideas?

[Zorgot.Crob]

I def. agree with the poster from Recording techniques. Using a single coil pickup would prob. be a viable way to capture EM disturbances.

[logey]

I should have been more specific and said "in the field" Whereas a single coil from a strat might work fine in the studio where I have preamps with intsrument level DIs built in, very few field recorders have enough gain to make this practical. I don't think my HD-P2 wouldn't get much out of a guitar PU. Is there an easy way to bring a guitar PU up to mic level? Something like a battery powered DI would do it I guess. Maybe I'll try that.

[Zorgot.Crob]

Something like a battery powered DI would do it I guess.

yeah, thats what I would do.

[apropos of nothing]

Anything with a gain knob ought do the trick. I've used a crappy cable placed near a monitor plugged into a Moog lowpass filter, or into a ProCo Rat. Crank the gain, and away you go.

[philbo]

Hard to tell what the headphones are listening for.

A Sony Walkman set to AM would qualify as an EMI sniffer for frequencies of 1 MHz (+/- 500 KHz or so).

To really do it right, you'd need a radio receiver that would be able to listen to everything from DC to microwave, sorting out what signals are likely to be of the type that interfere with your equipment (or whatever it is you are trying to determine).

Of course, if you are just looking for cool and unusual sounds, any shortwave receiver will provide lots and lots of those.
________
Box Vaporizer

[Bill @ Irie Lab]

Loogie,

You can make a "contact mic" to record electric fields (like from a refriderator or a fan) from the telephone headset contact pick-ups that you can get a RatShack.

Not long sitance but a way to capture an appliance's inner voice.

Bill

[logey]

Philbo - I'm not trying to sniff out problem noise, but rather record the sounds for creative purposes. Some of them can be very musical sounding. As far as shortwave reciever goes, I've got a great 1946 National reciever that picks up all kinds of great noise, but it weighs about 50 lbs. so its not an option for a portable rig. Unfortunately, a lot of the modern shortwave recievers have digital tuners and noise suppression so its not possible to get the noise in between the signal.

Bill - I have a number of contact mics that I've used for just such purposes, but they tend to pick up the mechanical sound of the unit more so than the radiation. Are you suggesting just getting it close to the source of the radiation and not making contact?

Does anyone know how to make a directional antennae?

[Bill @ Irie Lab]

Logey,

I was a bit imprecise in my use of the term 'contact mic'. What I was referring to is a gadget that picks up EM fields when in close proximity to the source, to be captured, amplified, and recorded by audio gear.

Here is what I was speaking of - from the RatShack site: http://www.radioshack.com/search/index. ... e%20pickup

As to directional antennae check the web sites for ham radio operators - they are DIY guys like us and should have plans for antennae (by frequency) that you can make from lawn chair aluminum. (maybe ). They will be a resource in any event.

Plz, post or link to some MP3s when your project is ready to share.

Good luck!

Bill

[logey]

Ahhh...yeah, I thought you meant a piezo type contact. Thanks for the idea, I'll give that a shot.
I did look into building a yagi type antennae, but it seemed like overkill.
Thanks for all the suggestions...I'll definately let you know if it becomes anything more than an idea.

[crowley]

Suggest the following

20+ turn wire loop about 3 inches in diameter, Connect both ends to the 8 Ohm side of a radio shack 8 Ohm to 1 K Ohm $2.98 transformer. Connect the other two leads (clip out the middle) to a phono lug into a little preamp or headphone amp. That will make a directional loop with a null and will pick up lots of interesting sounds and won't hiss or produce white noise. Cool and also bad tones from DVD players, notebooks, switches. Nice and portable. Explore the hidden world of EMI Feng Shui. Easy to do. Can be made much smaller if your amp has gain.

If you need it to be nondirectional, or less directional, you can "ruin it" by making a messy wind all over a tennis ball, or something.


http://microphonium.blogspot.com

Bob Crowley
One-Half of Crowley and Tripp

[logey]

Wow, Thanks Bob...I was envisioning something along these lines, but I couldn't wrap my head around the details. especially the transformer. I think I've seen directional antennae with the coil you describe wrapped around some sort of shaft. I'm thinking that this would make it much easier to point. Would I want this shaft to be conductive, like aluminum? or would it be better to make it out of wood?

Thanks...I'm definately going to try this.

Boyd

[crowley]

I'd make it out of wood or something nonconductive. Actually if you make a circly loop sort of like a little bird's nest, wrap it around and around, you can just use the wire to support itself if you want. Even a paper cup is a good coil form. Give it some diameter - maybe a couple of inches or three - and it will pick up hum and all those sounds linked above and more like crazy. You could even hide it in your sleeve, near your wrist, go around town sensing the different fields and grabbing them with a field recorder.

I think you could make this work another interesting way, by having the coil around your upper arm, then reach out to the source (be careful though). Maybe the basis for some performance art.


Bob



http://microphonium.blogspot.com

Bob Crowley
One Half of Crowley and Tripp

[logey]

You could even hide it in your sleeve, near your wrist, go around town sensing the different fields and grabbing them with a field recorder.

Thats a great idea Bob...wearing it around your wrist would allow you to orient it without having to hold it in your hand...2 free hands is almost twice as good as 1! It would also save the odd and suspicious looks you get from paranoid people when roaming around the city with any piece of unfamiliar equipment these days ("What's he doing? I don't know, but Its not something I understand...better call the FBI just to be safe!")
Would having the wire in contact with your skin ground out the signal at all? If not, then this is the way to go.

Thanks.

[mnotaro]

If I meet her I'm gonna copyright her EM radiation.