What is Acoustic Superconductivity

[INRM]

I heard it mentioned on a site and I want to know whether it's true or false.

 

[casebro]

context?

My guess is it would be something that conducts sound at supersonic speeds. Like water, which conducts sound faster than air does.

 

[Dr Adequate]

It seems to be a not-very-well-worked-out idea of Jerry Decker and the "free energy" crowd on keelynet.

If someone tries to sell you some acoustic superconductivity, be extremely cautious.

 

[Thing]

A few acousticians have used the term in a metaphorical sense to describe the very low losses that can occur over long distances in underwater acoustic propagation under the right conditions. And someone a while ago proposed what was essentially a microphone with a superconducting element, don't think it ever caught on. But for the keelynet crowd, as Dr A says, it's the usual [(sound = waves) & (electricity = waves)] -> (magical effects no one's observed) -> (gimme a dollar).

[ETA:Casebro, at the risk of being pedantic, superconduction has low resistance, not high velocity. Alright, I'm a pedant.]

 

[Schneibster]

[(sound = waves) & (electricity = waves)] -> (magical effects no one's observed) -> (gimme a dollar)

Heh, yeah, pretty much.

 

[aggle-rithm]

Unless I'm mistaken, this implies the existence of a "coherent sound", in which sound waves act similarly to the way light waves act in a laser. It's a contradiction in terms. "Superconductivity" implies quantum effects, and there's nothing quantum about sound waves.

But I could be wrong. Anyone smarter than me want to comment?

 

[casebro]

[ETA:Casebro, at the risk of being pedantic, superconduction has low resistance, not high velocity. Alright, I'm a pedant.]

In electrical superconductivity, yes.

I'll take "Acoustic Superconductivity" for 200, Alex. Wherein, I suppose, less resistance = higher speed. Not the same with electons, since thay all travel at 186,000 furlongs per fortnight.

If you know you are being a pedant, can't you just STFU?

 

[aggle-rithm]

In electrical superconductivity, yes.

I'll take "Acoustic Superconductivity" for 200, Alex. Wherein, I suppose, less resistance = higher speed. Not the same with electons, since thay all travel at 186,000 furlongs per fortnight.

If you know you are being a pedant, can't you just STFU?

Well, since sound can't travel faster than sound, by definition, I would think resistance in this case refers to lack of signal loss over a long distance.

Doesn't matter, it's all pseudoscience anyway.

 

[Fnord]

Ignoring the causes of superconductivity for a moment, and the fact that acoustics is not a quantum phenomenon (ignore "phonons" for a moment, as well), one could assume that the term "Acoustic Superconductivity" refers more to an acoustic signal passing through a medium without becoming distorted or attenuated.

The first time I heard this phrase used was in Michigan State University's Physics department. It was tossed around rather carelessly, I might add.

The second time I heard this phrase was while in the U.S. Navy. A sonarman was relating his story about how he listened (via passive sonar) to the crew's voices from the U.S.S. Thresher as she passed crush depth "half a world away." Again, this was not a scientific discussion, but the usage seemed more appropriate.

So, IMHO, "Acoustic Superconductivity" is the passage of an acoustic signal, through a ducting medium, without distortion or attenuation of the original signal. This would be more science than woo.

Disclaimer: I'm not a sonarman or a physicist, just an ordinary electrical engineer. I occassionally work with sound systems.

And somtims my spelin ain't no gud, neether

 

[Thing]

If you know you are being a pedant, can't you just STFU?

Because I'm right?
Acoustic resistance (viscous dissipation, thermal losses etc) doesn't slow sound down appreciably, it attenuates its amplitude.

 

[Cuddles]

I was going to go with some kind of technical explanation involving phonons, but I think the response "Wooooo" is more appropriate. Superconductivity means that loss is identically zero. Not "close to zero" or "fairly low", exactly zero. As far as I'm aware this is simply not possible with sound, therefore any talk about acoustic superconducting is either sloppy wording or just plain bollocks.

Alternatively, it refers to the sound you hear when you stick your head in a bucket of liquid helium.

 

[Big Al]

Alternatively, it refers to the sound you hear when you stick your head in a bucket of liquid helium.

Unless the helium were superfluid - then it would crawl up the sides and out of the bucket.

Otherwise, I imagine your eardrums freezing and shattering in an instant would make the audio experience a little limited.

OK - naughty pedant! [smack]OUCH![/smack]