The Sound of cold.

[Cogman]

a freezer uses sound waves instead of a compressor to comress helium to extract the heat and then cool the system.

Heres my question. How energy efficiant do you guys think it would be? And also arnt these two phrases contridicting? "But we can't hear the ultra-loud sound waves that cause this expansion and compression", "If you could actually be inside of the machine it would be much louder than the loudest sound that that I can even think of?louder than a jet airplane"

 

[Matthias99]

you suck at teh linking

No idea on efficiency. But I'm guessing you couldn't "hear" it because the frequency is too low -- humans can't hear sounds below 20Hz or so.

 

[glugglug]

Why helium?

The energy involved (on a per-volume basis) in the compression/decompression of Helium is less than that of any other gas except hydrogen. Also, the small molecule size makes it more likely to leak out. Xenon would have made a lot more sense IMO.

Also, I can't imagine the amount of cooling being substantial, or it being efficient. (I'd wager on it being more environmentally unfriendly than a conventional freezer in fact because of the energy use). In fact the low frequency of the compression/decrompression cycle and lack of a phase change (involving a hell of a lot more energy than just gas compression) ensures that this is not suitable for larger scale cooling a.k.a. air conditioning.

 

[Shalmanese]

your saying because of the high amplitude, it would sound "loud"? Loudness is a function of how much the ear follicles are stimulated. There are not follicles tuned to be stimulated at sub 20Hz so you wouldn't be able to hear that sound via your ears. You may be able to feel the bass effect through your body but that would just feel like your normal compression/decompression.

 

[glugglug]

No, in the article they said it would be incredibly loud if you were inside it. Outside the compressor it is silent.

Also, the 20Hz/20kHz limits of human hearing are not sudden dropoffs, the perceived volume based on pitch is a bell curve with the peak at 4kHz (the pitch of a baby's cry). At around 20Hz/20kHz this curve is low enough that it takes a really high amplitude for us to notice it, but if it is loud enough, you still can. I could hear the 80kHz tone I generated with my old Apple //gs for killing moths if I cranked it up more than halfway to max on the crappy internal speaker.

 

[Tiamat]

Originally posted by: glugglug
No, in the article they said it would be incredibly loud if you were inside it. Outside the compressor it is silent.

Also, the 20Hz/20kHz limits of human hearing are not sudden dropoffs, the perceived volume based on pitch is a bell curve with the peak at 4kHz (the pitch of a baby's cry). At around 20Hz/20kHz this curve is low enough that it takes a really high amplitude for us to notice it, but if it is loud enough, you still can. I could hear the 80kHz tone I generated with my old Apple //gs for killing moths if I cranked it up more than halfway to max on the crappy internal speaker.

I didnt know 80khz kills moths. I gotta try that sometime

Im the same way with sub-20hz as well. I can discern distinctive pitches down to at least 16hz. But this is comming from a 64ft pipe of a mammoth pipe organ with me sitting 5 feet from the mouth of this enormous pipe. BTW, it is a stopped flute, so its actually more like 32ft in length with a stopped top.

 

[Cogman]

now im kindof interested in the moth killing computer . I had some friends that would scream at Wasps, and They said if they did it high enough and loud enough, they would kill the wasp.

 

[f95toli]

No one can hear 80 kHz,. I've heard of people (kids) that can hear 25 kHz but that is about max (for a "normal" adult the limit is aroung 16-17 kHz).

The reason why you "hear" 80 kHz is because of distortion, what you hear is acutally subharmonics of the 80 kHz fundamental. There are very few speakers that can reproduce 80 kHz (most tweeters will start to roll off at around 25 kHz), but some speakers actually have tweeters that can go up to 100 kHz without breakup (I think the JMLab berylliym tweeter which you find in their "Utopia" speakers is one example).

 

[glugglug]

It doesn't kill them all by itself. The 80kHz makes them drop to the ground. (Instinct to avoid radar of bats). This makes it easier to step on them.

 

[Tiamat]

Originally posted by: glugglug
It doesn't kill them all by itself. The 80kHz makes them drop to the ground. (Instinct to avoid radar of bats). This makes it easier to step on them.

good enough for my standards, thanks for the info! :thumbsup:

 

[uart]

Does anyone know just how lower an audio frequency is used in this accoustic refrigerator? Any guesses at what frequency range they're using?

 

[TStep]

I would be curious as to how the sound is insulated from the outside enviroment. I would have to believe it must produce an out of phase wave of partial strength to cancel exterior sound generated.

 

[wfbberzerker]

Originally posted by: Tiamat

Originally posted by: glugglug
It doesn't kill them all by itself. The 80kHz makes them drop to the ground. (Instinct to avoid radar of bats). This makes it easier to step on them.

good enough for my standards, thanks for the info! :thumbsup:

come on now! if youre gonna get technical, its sonar