First up is Dan Hemingson's "ambisonic" (Wikipedia) recording work. Shown above is the tetrahedral microphone array Dan uses to record his soundscapes, three of which he played back on the ACTlab's surround-sound system. The tetrahedral microphone arrangement makes it possible to mathematically derive any number or spatial arrangement of surround-sound channels from the raw audio. Professional ambisonic microphones cost thousands of dollars; Dan put his together for nine bucks.
For more information on soundfield mics, visit:
en.wikipedia.org / wiki / Soundfield_microphone
(I am not allowed to post links, so you will have to knit these together.)
Note that the cheapest, from Core Sound, is about $1000. This is a lot less than "thousands of dollars", but a lot more than $9.
For more information on home build soundfield mics, visit:
www . ambisonia . com / wiki / index.php / Microphones # Home_made_tetrahedrons
(Again, you will have to knit it together.)
Regards,
Martin