[PSUBS-MAILIST] Bizarre idea of the week: 16 January to 22 January 2006

[Michael Holt <mholt@ohiohills.com>]

SOUND CAMERA


A balloon full of carbon dioxide acts as a "sound lens". If you fill a 
fairly large balloon with CO2 and place a microphone at the right spot, 
it will act as a long-range listening device. But being a lens, the 
balloon actually creates a "sound image" at the focal plane. So, why not 
build a camera to detect this image? Place a row of closely-spaced 
microphones on the surface of a rotating drum. Give the drum some 
circuitry to amplify the sound from each mike and have the received 
sound signal drive an LED. If you place each LED on the opposite side of 
the drum from each microphone, then any sound that "shines" upon one 
side of the drum will become patterns of light on the other side. Maybe 
give each channel a low-cut filter, so it will only "see" the 
sharply-focused high frequencies. Now "illuminate" the room with a 
high-pitched white noise. This mimics white light and eliminates 
diffraction fringes and "laser speckle" effects. Spin the drum, aim the 
lens, and see what "acoustic scene" appears on the raster of moving LEDs.

Now if you built an UNDERWATER version of this, then you'd have a camera 
that could see through muddy water 
<http://www.apl.washington.edu/programs/DIDSON/Pages/LIMIS.html> (maybe 
even see through mud and sand.) Water-filled human flesh would look 
almost invisible, and people would look like living skeletons covered 
with clear-jelly muscles, except for their silvery air-filled lungs and 
tracheas. And don't forget blobs of silver-reflective gas in their 
intestines.

http://amasci.com/freenrg/ideas.html#cam




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