Topband: Extreme directivity

[Jim Brown]

On Sun, 22 Jul 2007 20:51:31 -0700, Michael Tope wrote:

>The only reason the ultrasonic system works is that there is a non-linear
>interaction between the ear and air around it that effectively demodulates
>the signal. The important thing to understand is that the energy propagates
>from the speaker to the listener as a modulated ultrasonic wave, so the
>properties of air in the ultrasonic regime dictate the propagation
>characteristics.

Yes. AND -- pro audio is the world where I work. This ultrasonic concept was 
demonstrated at least 20 years ago, but I don't know of any use of the technique 
in real world systems. One of the problems is getting ENOUGH sound for a price 
that doesn't break the bank, and doesn't have other problems. In other words, 
the article quoted may be valid science, but probably not a practical product 
(or may be based on the press release from a company who hopes it will be a 
practical product). I've seen a lot of that over the years. :)

73,

Jim K9YC