Start with two audio amplifiers, each with its own speaker -- a computer is programmed to control this special sound system. Place one speaker 150 ft. in front of you, the other 150 ft. behind. One amplifier plays the word “Half”, the other the word “Bakery”. The sounds take a moment to travel. The amps are synchronized so that you hear the word “Halfbakery” where you're standing. Now try this experiment with two additional amps & speakers, placed to your left and right. Each speaker plays only one syllable of “Half-Ba-ke-ry”. The sounds will form the word at your position. Move or add speakers, farther or closer, play longer messages, and program the synchronizer to adjust. Now have the system chop the sounds into even smaller bits. The various short bursts from the speakers won’t make sense unless you’re standing at the point of convergence, where you’ll hear the complete audio. Scramble the speaker patterns, use odd electronic signal phasing, add a “pink noise” hiss – make it even more alien to bystanders, and still crystal clear to the target listener. It might be possible to encode your message into an otherwise ordinary song! Since this is a “private message” of sorts, maybe it’s at a certain tile in a public place where you’d stand to hear affirmations, your fortune, etc.-- Amos Kito, Jun 06 2003 HyperSonic Sound http://www.atcsd.com/tl_hss.htmlSame effect, different technology [-alx, Oct 04 2004, last modified Oct 21 2004] Quadrophonic Crescent.-- thumbwax, Jun 06 2003 I love this idea.-- JRandMoby, Jun 06 2003 I have a bizarre feeling that this has been baked but no evidence 4 it, racking the dark recesses of my brain!-- PiledHigherandDeeper, Jun 06 2003 Similar things have been done with dual radiation beams for cancer treatment, the point where you cross the beams gets a much higher dosage and killds the tumour-- PiledHigherandDeeper, Jun 06 2003 The 'private message' type thing has achieved using a different technology, which lets you point a highly directional sound beam at someone. See link.
That said, I like this idea, as it doesn't need any particularly sophisticated hardware.-- -alx, Jun 06 2003 Oooooooh, make it a Hypersonic Crescent, then.-- thumbwax, Jun 06 2003 Hang on. Shirley in the two speaker example you won't hear the word "Halfbakery" as if it's emanating from the spot where you are standing? Assuming you have two fully functional ears, you'll just hear "half" coming from one speaker and "bakery" coming from the other speaker. If you're not in the right spot, you will hear "HALF" from one and <arena>"bbaakkeerryy" from the other. Or vice versa. Given this, I can't see how adding more speakers would give the effect you intend.-- egbert, Jun 06 2003 random, halfbakery