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How parabolas really work

Subject: How parabolas really work
From: Marty Michener <>
Date: Tue, 18 Feb 2003 08:34:20 -0500
HI:

Ok, those of you who still want to visualize how parabolic reflectors 
convert a distribution of distant sound sources into focal plane microphone 
placement, here are the photos you asked for of the red and green bulbs and 
the shiny parabolic reflector, and then the image on the wall.

Here is the picture of the battery, reflector and two bulbs, about 7 mm 
apart.  The angle arctan 7 / 33 comes out to about 12 degrees, placing the 
red and green blobs on the wall (@ 30 ") about 7 inches apart, very roughly.

http://www.enjoybirds.com/howitworks/twinsetup.jpg

Here is the image on the white plaster wall.  It is messy for the same 
reason our sound patterns are messy, because the reflector is for 
practically reflecting a carbide lamp flame, not a perfect optical image.

http://www.enjoybirds.com/howitworks/wall.jpg

As I stood behind the reflector rig, the red bulb was on my left; the red 
blob on the wall was on my right.

BTW total time spent about 1 hour, including buying, rigging, photos and 
uploading.

Enjoy.    my best regards,


Marty Michener
MIST Software Associates PO Box 269, Hollis, NH 03049

EnjoyBirds.com  - Software that migrates with you.    http://www.EnjoyBirds.com



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