🚀 go-pugleaf

Here is a summary of what I found out:

From V105L4LG@ubvmsc.cc.buffalo.edu:
                I got some ultrasonic tranducers to buy at a small electronics
place out in Nassau county/Levitt town,the business place is called Edlie
electronics check out the phone book. Sorry no # I don't have much with me here,check out the phone book he is listed.        Price around $15.per

From George P Cotsonas <geopi@hocpa.att.com>:
About 8 years ago, Polaroid had these little ultrasonic modules,
which could be had in the form of evaluation boards (~$200), which basically
measured the time delay of ultrasonic pulses returned from the environment;
intent was autofocus cameras.

I see digital tape measures in the hardware store bargain bin these days,
which use the same technology at only about $19.

Thanks for the replies.  I've also found that DigiKey has ultrasonic sensors
from Murata Erie North America (DigiKey: 1 (800) 344-4538)

Frank Koss
fk06@andrew.cmu.edu
    or
koss@cs.cmu.edu