Someone posted a few messages about this http://www.straightdope.com/classics/a2_114.html
and left out the link to the classic column being referred to, and made errors in their first two posts. In trying to delete the error messages, I accidentally deleted the thread. Care to post again?
Sorry bout that.
Jill
Didn’t catch the 1st 2 posts but I remember of hearing about an audio equlivant of the laser as a device that emits a single tone. were not talking about a tuning fork here but something with a much smaller bandwidth possibly finite. they were round disks hooked up to some amplifier mechism, (no they were not symbols). also I’v seen sound waves suspend objects.
I just saw Kundun on cable and it occured to me after reading this column that all those supposed ‘pacifist’ monks are chanting really low and all on key are trying to nuke us with sound waves!
(13 octaves below Middle-C, all together in a cone shaped building!!)
Good golly… you even have to watch out for pacifists! I wonder if the south would be protected from attack by all that cotton?
If you think I’m whacky, wait for the HARP guys to show up on this topic…
I gotta go… I’m hearing a hum… INCOMING!
Fear not, UnderDog. It is not the drone of intercontinental ballistic lamas you hear – and fear – but the harmonic convergence of your refrigerator, dishwasher, air conditioner, electric razor, hard drive, coffee mill, food processor, stereo receiver, electric toothbrush, microwave and the residue of the bad acid you dropped at Woodstock.
Since No Llamas have impacted on my gazebo I can safely say you were right (but not about the acid)
All joking (well most) Since sound is basically a mechanical force (moving airwaves) and the physical principle of adding and directing vectors of force, it just ‘seems’ like you could get sound going more or less one way through proper reflection in a confined space, and, if it’s acoustically ‘good enough’ could really get some vibrations going along a plane or even a line. Probably only at really low temperaturs though or air molecules would be spinning and bumping around so much it’d be like pointing a high pressure air hose into applesauce…messy and not coherent. Hmmm… much like my posts.
Okay, enough on this for now. I’m busy researching that artical about Parthenogenesis! Wild stuff!
Here’s a link to the original Audio Lasers thread, including my brilliant, witty, and in all ways perfect post.
Dogs love cheese
Relieved to hear it, UnderDog. They are gentle creatures (quite unlike the obstreperous alpacas and vicunas). I would hate to see them become part of some twisted new escalation of the arms race.
First of all, “laser” refers to the result of specific process. Even if one could duplicate the result in sound, the process would be different, so technically it wouldn’t be a laser.
But more importantly, sound is a wave. It’s just not possible to focus a wave from a particular point into one particular direction. The wave will just spread out. Think of that ever-ready analogy, ripples in a pond. If you drop a pebble into a pond, it will creates waves. You can put barries that will redirect those waves, but whatever you do, the waves will spread out once they get past those barriers. That’s what waves do.
Now, you’re probably thinking “But light is a wave. How can it be focused?” The answer is that since it has such a smaller wavelength than sound, it spreads out much less quickly, and for practical purposes it can be considered to be completely focused in one direction. But the Heisenberg principle tells us that if light were ever completely directed with absolute certainty in one direction, we would lose all knowledge of its position, and if its position were ever determined absolutely, we would have no knowledge whatsoever about its direction. Its small wavelength allows tradeoffs so that we can have quite a bit of knowledge about its position, and quite a bit of knowledge about its velocity, but imcomplete information in both areas.
Concerning audio lasers.
In a recent article (either in Science News or Scientific American), a technique was explained for receiving sound waves from a source, and playing them back AS RECEIVED. The result is retracing the sound waves path, so that they converge on the original source.
This has all sorts of possibilities.
Directional sound systems
Kidney stone removal (by playing back an amplified sound)
Audio illusions…
Heck, you could even build a security system that fires precisely targeted high frequencies if an intruder makes any noise (the next mission impossible? 
Anyway, this close enough to an audio laser for you guys?
Concerning audio lasers.
In a recent article (either in Science News or Scientific American), a technique was explained for receiving sound waves from a source, and playing them back AS RECEIVED. The result is retracing the sound waves path, so that they converge on the original source.
This has all sorts of possibilities.
Directional sound systems
Kidney stone removal (by playing back an amplified sound)
Audio illusions…
Heck, you could even build a security system that fires precisely targeted high frequencies if an intruder makes any noise (the next mission impossible?
Anyway, this close enough to an audio laser for you guys?