Directed Sound

yawningyellowyak writes "Technology Review has an interesting article on directed sound. Ultrasonic 'sound' is sent out from a 'speaker' and the distortion encountered on hitting the air produces hearable sound, but only in certain spots. You could be standing right next to someone and they would hear nothing. One step closer to the cone of silence!"

Comments

A sea of calm

[the_twisted_pair]

It would be simple to defeat though. The effect relies on heterodyning a signal (mixing HF to produce an intermodulation effect) so broadcasting white noise above the range of hearing should drown the wanted signal nicely - just like interference on an AM radio. Say a small device located near the billboard - or two piezo drivers on the outside of headphones, heck you could build it into your cellphone hands-free kit.

Done well, you wouldn't hear a thing; even partial cancellation should reduce the adspeak into something akin to a distant ocean sound.

I think there would be privacy isues to overcome on the part of the Admen first however - remember the hoo-haa over subliminal advertising?

Re:Can I smell something ?

[raygundan]

Yeah, this particular little invention is what really drove the concept of "vapourware" home for me. I read about it first while I was in college, back in *1998*. I followed it excitedly, because at the time it was touted as a lightweight, low-power, flat-frequency-response speaker system. The directionality was just a side effect. Turns out it's not all it's cracked up to be in the audio quality department, but hey... that side effect is still there six years later, so let's capitalize on that instead!

As I tried to keep up with who was developing what with the tech (it's been licensed over and over, but nobody's ever built anything commercially available) I got more and more depressed with the whole thing. And I learned an important life lesson... until you can click "Buy Now," (and sometimes not even then) it may as well not exist unless you intend to build your own from a copy of the patent. I try to just ignore announcements like "Hypersonic Sound" now.