Is there a sonic equivalent of a laser? If not, could one be made?
IIRC, and I don’t recall where but quite recently, they have just found a way to do it, but it needs some more development. Those on Board of a more scientifc bent can give you more details.
Vibrational quanta in a crystalline solid are called phonons. Since vibrations of the crystalline lattice are the way sounds are transferred through solids, I can argue that a resonator that takes advantage of these quanta, forming a resonant cavity using these, is the “sound” analogue of a laser. There were two papers in the journal ** Physica Status Solidi** back in the mid-80s devoted to such a device, which the authors dubbed a “Phaser”. I still wonder if they were Trekkies. The papers were theoretical – I don’t know if anyone ever tried to build one of their Phasers. But the papers suggested it would be very hard, if not impossible – you’d need extremely regular crystals, with incredible low levels of impurities.
As an aside, I note that the “Feedback” you get when setting up an audio system with microphone and speakers is a wonderful sonic analogue to a laser. Feedback is caused by sound of a certain frequency from the speaker being fed back into the microphone, which causes the volume coming from the speaker to increase, which causes more sound from the speaker, in an endless loop until you get an ear-splitting shriek from the speaker. Just as in a laser, the sound builds up from random noise already present in the resonator system, and the frequency is determined by the physical dimensions of the resonator (microphone-to-speaker distance) and the frequency response of the system (you won’t get feedback at frequencies the system doesn’t reproduce well, which is why you suppress those frequencies on your sound board when you do a Sound Check). You can also “seed” either a laser or a sonic feedback system (just whistle into the microphone at the feedback frequency to get it started). In each case, the energy that drives the amplification has to be fed in from outside. The only difference is that the energy isn’t directional in your speaker feedback system. And,unless you’ve got a KILLER sound system, it won’t cut through metal.
there are sonic devices designed to emit a solid single tone. I have heard of them being refered to the anology to lasers but there was no focusing of the sound waves.
Don’t dolphins do something similar? I read (ok, saw on tv) how they stun prey with sound.
Peace,
mangeorge
Alright, just a minute. I have a small problem in the idea converting a wave into a particle energy form. Sound is a group of particles that knock into each other and have relative movement to each other which we call sound waves. The energy disburses throughout a multitude of particles not only the intitial particles. If I were to turn on my stereo it causes the matter in the coffee in my cup to bounce around in a similar fashion of the output of my music. When the sun shines in my face I do not fly at the ground at the speed of light or even a fraction of that. If I had a sound wave that could be produced from my throat with the power of light, I could melt buildings. The laws of motion play a larger part in the kinetics of sound than that of light. In light and lasers, the energy is mostly still around the original particles. The only way I could see and sonic equivalent of the laser would be with uniform movement as the earlier crystals before mentioned because if that matter vibrated on one axis and continuously reorganized itself into one direction (basically a bouncy ball in a small tube) and the kinetic energy was high enough to stay with the matter a while longer, and the matter would have to be in a vacuum, it might be a laser. Then again it is still kinda a high powered echo.
Agreed DJDeMarco…
Sound is a pressure wave propagated through a medium (be it gas, liquid, or solid). A laser consists of particles that are independent of the medium that they are traveling through. There is no such thing as a “phonon” as a discrete particle, purely as a mathematical abstraction.
I think the intent of the question (if I hazard) may have been referring to the columnar “beam” characteristic of a laser and whether sound could be projected in a similar fashion. In that case, yes. A good parabolic reflector is all that is needed (while also making sure that the vertex of the parabola is of the proper proprtional lenght to a pure tone wavelength that any destructive harmonics aren’t created).
I’ve been warned about the dangers of disputing your veracity here Cal, and as such, it is very humbly that I venture to do so, but when you “Ring Out” a system in sound check you are actually doing the opposite of what you suggest here.
The idea is to raise the over all system output till you get feedback (thereby identifying the frequencies that have acoustical spikes), then using equalization, you attenuate (reduce) the frequencies which the system (or the room, as often as not) exaggerates.
I’m not really sure whether you made an acoustical error, a structural one in your sentence, or just a brainfart. Then theres always the possibility that I am missing something.
humbly
CJ
Didn’t I read something in Popular Science a few years ago about a conch-shaped metal encasement built by MIT or something that could amplify sound waves to levels so high they could cut through metal?
–Tim
Bad Hat:
Don’t worry about tellin’ me I’ wrong. I do it all the time. It’s only when people tell you you’re wrong that you learn. I’ve never done a sound check (I’ve watched them, though. My wife used to be part of a concert organzation.), so I bow to the experience of someone who HAS done them.
That said, though, I don’t see how your statement iffers from mine. You identify the acoustic frequencies that have spikes due to fedback, thn you suppress those frequencies because you DONT want feedback. It seems to me that this is what we both said. You certainl don’t want to raise th feedback at those fequencies, or even leave them as they are, if you want to have a chance of listening to the concert. Of course, you would want to raise the feedback if yo wanted to build an analog to a laser system. But most people don’t like having their ears basted.
Cal,
It sounds like we actually are on the same page, where I think its got messy for me was:
When you said “frequencies a system doesn’t reproduce very well”, I inferred your statement to mean frequencies that a system underproduces (dips). Of course its perfectly valid to say the opposite, that if a system reproduces a frequency too LOUDLY (spikes), it obviously is also not reproducing it very well (accurately).
I’m there.
CJ