🚀 go-pugleaf

In article <24493@unix.cis.pitt.edu> fmgst@unix.cis.pitt.edu (Filip Gieszczykiewicz) writes:

	   Greetings. What do you people think of using sound waves
	   as a transmission medium. I think that anything below
	   10 KHz would have problems with background noise (pumps,
	   60 Hz, etc.) but anything above 40-50 KHz should work
	   just fine. Does anyone see any problems with this?

I've thought of using sound waves for robotic applications a few times
but so far haven't done too much about it. The main problem with
anything <20K is that it going to drive every person/dog/cat in the
vecinity crazy.

Higher frequencies (ultrasonics) are of course used a great deal for
obstacle detection / range finders. We have some very cheap
transducers (2.5 UK pounds each) that although not exectly high
performance devices do, are quite capable of detecting resonably sized
objects up to about 2 meters away. These opperate at 40KHz.

The main feature of sound waves at these sorts of frequencies is that
they are reasonably directional and rapidly attenuated; which is why
they are so useful as obstacle detectors / range finders. I think you
need some quite significant power output (compared with the usual
transducers) to get any ranges above a few meters. As far as I
remember from my physics wave like propogation in air is quite
restricted in its frequency range, and the high the freq the more
rapid the attenuation.

Having said all that I'm still quite keen on using sound waves for all
sorts of things. We have a digitising device around that uses a sparc
to generate a sound pulse which is timed by two sensors about 50cm
apart to give position. These used be quite popular a few years back
as low cost digitising tablets; I guess mice etc killed them off.

I've also seen it suggest on a TV sience program (tommorows world),
that a similar principle could be used on a larger scale. They showed
a room with microphones in the corners. Using these a clicking
transmitter could be traced in 3D to an accuracy of about 1cm by
timing the arival of the pulses. Trouble is I can't remember who was
doing this, sounded like a system that would be fun to setup. I guess
in many environments the problems of interfering sound sources would
be quite significant though.

Anyone else got ideas on the use of sound. I get the feeling that like
other senses sound has been a little neglected in the rush to show
what large amounts of computing power vision requires.
-- 
		   -- Michael Stevens --
Dept. of Engineering			Univerity of Warwick, Coventry, England