You wrote;
> Although I could've sworn something was posted to KeelyNet recently
> about creating and detecting sonic waves well into the MHz range. Or
> maybe I'm thinking about the file on collisionless shockwaves. Damnit.
> Help me out here, Jerry!
As a matter of FACT, air can be vibrated well into the MEGAHERTZ range.
The argument becomes where does the word acoustic stop? At what
frequency?
Human hearing which is generally from 13khz to 15khz...that's what I
prefer. Anything beyond that is still modulating air, such as
ultrasonice up to 60hkz or so, though generally around 30khz..
Olympus Corporation makes and SELLS a 'scanning acoustic microscope' that
uses a crystal shaped cavity that focusses intense vibrations to a very
fine point IN THE MHZ range, they say specifically 6MHZ.....this tiny
point of vibrating air is reflected back and builds up a 2 dimensional
microscopic image of the material being scanned.
This acoustic microscope was put on the market about 8 years ago, at
least and I was totally amazed at the time that air could in fact be
modulated at such a high frequency...I always thought the elastic rebound
property of air must SURELY put a limit on how high it could go, so I was
thinking maybe 100khz max...surprised, I was (as Yoda says)....
-- Jerry W. Decker / jdecker@keelynet.com http://keelynet.com / "From an Art to a Science" Voice : (214) 324-8741 / FAX : (214) 324-8741 KeelyNet - PO BOX 870716 - Mesquite - Republic of Texas - 75187