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I'm planning some experiments with non-conventional sound receivers and I've seen some piezo- and hydrophone experiments here but nothing with phototransistors or geophones. These don't work? Or has no one tried yet? And are there any other sound pickup devices that I've not thought about? I have done some experiments with a magnetic coil pickup and with AM-radio's tuned between stations. Any other ideas or experiences?

A few samples made with the pickup coil:

http://www.freesound.org/samplesViewSingle.php?id=65286
http://www.freesound.org/samplesViewSingle.php?id=65392
http://www.freesound.org/samplesViewSingle.php?id=89289

And the AM radio:

http://www.freesound.org/samplesViewSingle.php?id=65393

But probably it's possible to get much weirder / more interesting sounds this way. Any samples I could learn from?

Anyone with a police band receiver should be able to get interesting beeps and squeaks from weather satellites etc. When I was young, I used to love listening to shortwave radio and hearing all the morse code traffic and other beeps and squeaks on there. My first thought when I began recording sounds, was to record all of that, particularly as another sound effects library used shortwave radio signals as the basis for sci fi content. Unfortunately I discovered that it's all gone. The airwaves are pretty much barron now, nothing but radio stations and who wants to listen to them?

O yeah and what's a phototransistor?

JustinMacleod
what's a phototransistor?

But what do they have to do with the recording of sound?

JustinMacleod
But what do they have to do with the recording of sound?

Alternatively look here.

Woops. Don't know how but completely missed the link. Sorry. :$

Hello uair01,

Always nice to know someone is planning "non-conventional" recordings
I have made some very non-conventional recordings myself and I am always keen to listen to other people's. Please post once available.

You seem to have all bases covered, but nevertheless, some suggestions.

CONTACT MICS
I have made some recordings using contact mics, and homemade contact mics build from piezo transducers.
For example
http://www.freesound.org/packsViewSingle.php?id=5744
These work great if attached to an object to work as ressonator. Of course, try different sounds, but also try different objects.
For example: set your mobile to vibrate and put it on the table.
Try recording the sound with a contact mic on the table (if not able to attach it to the table, try putting a heaVy book on top of it)
Also try recording the same sound with the contact mic attached to a plastic cup (one of those discardable plastic cups will do great).
As for means of attaching the contact mics, here are a few ideas.
Most purchased contact mics have a clip. Piezo discs can be attached using clothes pegs or glue tack. Sometimes just putting a heavy object to hold them in place will do.

COILS
Try different coils. Scavenge broken electronic devices for coils or wind your own.
Use shielded cable to connect the coil to the amplifier/recorder, otherwise the cable itself may pickup noise. Although this may actually produce interesting sounds, having a small coil at the end of a shielded cable will allow you to use it as a sensor to pickup electromagnetic noise from different devices.
Listen to what you can pickup around TV sets, computers, laptops (these are great!), CD and DVD players, mp3 player (also one of my favorites! try start/pause/stop...). Also try washing machines, fluorescent lamps, phone cables, transformers...
http://www.freesound.org/packsViewSingle.php?id=5822
A music that uses some of these coil sounds can be found here:
http://www.myspace.com/thealienxxx

MICROPHONES
There is the old trick of using a speaker as a micrphone. I am sure you have tried that.
You can get different sounds from the same microphone by inserting it into different objects (cups, tubes, plastic bottles...). Usually you want the microphone inside the object but not touching it.
Here is an interesting one for you to try:
Connect your mic to your stereo. Set volume to zero.
Switch the stereo on. With the mic open, gradually increase the volume from the speakers until you get feedback. Now turn it down a notch.
Grab a can or a cup and slowly insert it over the mic - be very careful not to touch the mic. The ideal is if you can do this with one hand and keep the other one on the volume knob (just in case).
You should start getting feedback again! - take the can out and the feedback disapears again.

IMAGES (??)
For computers, sound is just data. If computers can convert data to sound, any kind of data could be converted to sound.
I did some experiments not long ago on sound-to-image and image-to-sound conversion. Even used graphics programs to process sound. Search the forums and you will find the thread.
Here are some examples:
http://www.freesound.org/packsViewSingle.php?id=5447

Happy to discuss, share files, collaborate. Send me a private message if you want.