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Science Technology

Refrigerators To Cool With Sound (Cool!) 446

Posted by timothy from the loud-food dept.
T-Kir writes "A very interesting report from the BBC where researchers at Penn State University are developing a prototype fridge that cools using metal plates and sound waves. If successful, this technology would help remove the dependance on gases that contribute to global warming. Talk about Cool!"
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Refrigerators To Cool With Sound (Cool!) More

Refrigerators To Cool With Sound (Cool!)

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  • But... (Score:5, Funny)

    by Telastyn ( 206146 ) on Wednesday December 04, 2002 @01:57PM (#4811424)
    Reduce the gases that contribute to global warming, but contribute to noises that drive Fido mad...

    </senseless humour>

    • Re:But... (Score:5, Interesting)

      by homer_ca ( 144738 ) on Wednesday December 04, 2002 @02:06PM (#4811514)
      I'd worry about my ears more than Fido's. The article doesn't say the frequencies are ultrasonic, so it's possible human ears will need protection too. I can't imagine how much sound insulation you'd need to hold in 173dB. What happens if the chiller doesn't cut off when you open the fridge door? I'm picturing the last scene of Raiders of the Lost Ark where the Nazis get their faces melted off.

      • Re:But... (Score:5, Informative)

        by Randolpho ( 628485 ) on Wednesday December 04, 2002 @02:13PM (#4811585) Homepage Journal
        The article specifically mentions that the sound intensity necessary can only be generated in a super-compressed gas. The sound wouldn't be audible to you at all. Or to your dog, for that matter. It would only exist inside the compression tube.

        • Re:But... (Score:4, Funny)

          by Anonymous Coward on Wednesday December 04, 2002 @02:40PM (#4811827)
          Bah! It's people like you that ruin perfectly good sensationalist speculation.

          This is Slashdot, take your "facts" and your "knowledge" to somewhere that cares. ;)

        • Re:But... (Score:5, Interesting)

          by homer_ca ( 144738 ) on Wednesday December 04, 2002 @03:01PM (#4812026)
          It says compressed gas is needed to generate the sound. All that means is if someone breaks open the fridge it won't keep making 173dB noise. However sound conducts through many materials, solid, liquid and gas. While the chiller is running, you'll still have to soundproof 173dB of noise while taking into account things like heat exchanger tubes.

          How's this for an experiment. Turn your stereo speakers up to the loudest (that's maybe 110dB if you have a killer stereo) and try to build a soundproof box around it that's smaller than your fridge.

          • Re:But... (Score:5, Interesting)

            by victim ( 30647 ) on Wednesday December 04, 2002 @03:38PM (#4812397)
            Not quite a proper analogy.
            • Shrink your speakers down to the size of soda can.
            • Realize that this thing operates at a specific frequency and set of harmonics. You are free to use all sorts of resonance tricks.
            • You never need to get inside. You can make a metal casting 23mm thick if you wish.
            • I don't recall reading that his operates in the 20-20kHz range. Maybe its above 20kHz so a small amount of sound leakage is tolerable. (Seems unlikely, but... high-low separation at 20kHz is a fraction of an inch at atmospheric pressure. At higher pressure the wavelength will be greater, so that might give enough space.)

            Suddenly it seems a lot easier to soundproof.

            There is also the issue of the density difference from the compressed gas media in the tube to atmospheric pressure (think about sound not transferring well from water to air or back), but I suspect that is a red herring given that you are going to a more dense material first before the atmosphere.

            Incidentally, I think they have a compressed gas because you can't do 173dB in free air. You rip the air down to total vacuum in the low pressure parts before you get there.

            Unrelated trivia note: Your hearing ends at 20Hz. If you put a mic on your body and pitch shift the 20Hz range up into audible frequencies you will find that your body is quite loud and distracting if you can hear it.

          • Re:But... (Score:3, Interesting)

            by Christopher Whitt ( 74084 )
            Look up impedance matching, particularly as it relates to sound transmission between differing media...

            Christopher


      • refregerators are one thing, but I see this being a good application for roof mounted HVAC equipment. which is noisy anyways and are usually mounted in remote locations. This also applies to most commercial walk freezers/coolers. They all use a remotely mounted condencing (cooling) unit. My biggest questions are 1.) weight 2.) power consumption. I imagine this would remove the need for a compresser and radiator type vents making it lighter.

      • Re:But... (Score:5, Funny)

        by istartedi ( 132515 ) on Wednesday December 04, 2002 @02:39PM (#4811811) Journal

        I'm pretty sure that Underwriter's Labs will reject an appliance that melts the user's face off everytime they use it. I've seen their checklist and "[x] make sure face doesn't melt" is on there. So, it will be hard to find any contractor who will install it, or any major department store that carries it.

      • We all know that ultra low frequencies can cause your bowels to, well, kick in and empty out, right? I wonder if you can buy a package deal - combo 'fridge/toilet. Kick in a TV, padded/heated seat on the toilet, and you've pretty much just created the ultimate guy Christmas present.
    • I thought that the gasses weren't used in NEW fridges, just the old ones.

  • Also on Scientific American (Score:5, Informative)

    by Tyrnagog ( 609616 ) on Wednesday December 04, 2002 @01:58PM (#4811432)
    Check out their article here. [sciam.com] Unfortunately, no mention of peoples' hair igniting.

  • excellent (Score:2, Funny)

    by enos ( 627034 )
    Now maybe people will believe me when I tell them my fridge tells me to eat too much...

  • Oh yeah... (Score:5, Funny)

    by WPIDalamar ( 122110 ) on Wednesday December 04, 2002 @01:59PM (#4811438) Homepage
    If my fridge were to emit some cool Barry White, that's be pretty ... well... cool.

    First there was the "Brown note" ... now the "cool note"

    • Re:Oh yeah... (Score:4, Funny)

      by cybermace5 ( 446439 ) <g.ryan@macetech.com> on Wednesday December 04, 2002 @02:30PM (#4811756) Homepage Journal
      My fridge *already* says "Baby, this your appetite speaking" whenever I look at it. Or at least that's what the voice in my stomach tells me.
      • Really? My fridge plays "Living in the fridge" [ncu.edu.tw] by Weird Al everytime I open it.

        OK, no it doesn't. But when I shared a flat with Dick [slashdot.org] we seriously thought about getting a small MP3-player, hook it to the fridge's door switch and rig it to play that song. We did put a bio-hazard sign on it, used Whiteboard pens on it to keep track if the fridge inventory and had thin Ethernet everywhere, including both toilets and the oil-cooled[1] MP3 server in the kitchen cupboard.

        [1] We kept a 5-liter (~1.25 gallons) can of cooking oil next to it, an old P75 running NT4 and Winamp with wires through the back wall to the living room stereo system. :-)

  • Cooool (Score:2, Informative)

    by p4ul13 ( 560810 )
    Sounds of 165 dB would cause a person's hair to catch fire from the frictional heating caused by air undergoing such intense compression and expansion.

    Thankfully, even if the fridge cracks open the vast sounds generated within will not escape because the intense noise can only be generated in the pressurised gas locked inside the cooling system. Thats a damn scary sounding (no pun) fridge!

    • Re:Cooool (Score:5, Funny)

      by JUSTONEMORELATTE ( 584508 ) on Wednesday December 04, 2002 @02:18PM (#4811651) Homepage
      Sounds of 165 dB would cause a person's hair to catch fire from the frictional heating caused by air undergoing such intense compression and expansion.
      Yeah, but what if I want to keep a human head in my fridge? Won't the hair catch fire and warm up the fava beans?
      --

  • Millions of dollars of research down the drain (Score:5, Funny)

    by Gorm the DBA ( 581373 ) on Wednesday December 04, 2002 @01:59PM (#4811443) Journal
    So, after all those Maytag commercials advertising that their product is the quietest ever...now they'll be advertising "The TURBOBLAST 9000!!! Generates 186 decibels of ear-splitting cooling power!!!!!".

    If this is so cool...how come my constantly loud neighbors haven't turned into icicles yet?

  • Fine... (Score:2)

    by wls ( 95790 )
    But will it be cheaper to build and cost less to operate. If not, doubt it will catch on.

  • who want's a fridge when you can do this? (Score:4, Funny)

    by anonymous loser ( 58627 ) on Wednesday December 04, 2002 @02:01PM (#4811460)
    Sounds of 165 dB would cause a person's hair to catch fire from the frictional heating caused by air undergoing such intense compression and expansion.

    You know, that sounds way more fun that cooling some ice cream. Or maybe I've been playing too many videogames.

  • I imagine... (Score:3, Funny)

    by Gudlyf ( 544445 ) <.moc.ketsilaer. .ta. .fyldug.> on Wednesday December 04, 2002 @02:01PM (#4811465) Homepage Journal
    ...that before long, we'll see this sort of thing cooling the insides of computers, totally doing away with those pesky noisy fans!

    Err wait a minute, they're cooling with sound...ummm nevermind. Move along.

  • Other ways to do this... (Score:5, Interesting)

    by Fnkmaster ( 89084 ) on Wednesday December 04, 2002 @02:01PM (#4811468)
    You can also make refrigerators using a Stirling-engine like gas compression cycle. The guys at Medis Technologies [medisel.com] have designed this. See here [medisel.com] for the brief description. I guess instead of trying to extract mechanical work from a Stirling engine, they are just removing heat from one area and piping it off elsewhere. They claim this uses no greenhouse depleting gases, and it sounds plausible to me.

    • That's what this is. (Score:4, Interesting)

      by benjamindees ( 441808 ) on Wednesday December 04, 2002 @02:20PM (#4811673) Homepage
      It was developed at Los Alamos [lanl.gov].
    • I seem to remember that Einstein took out a patent on a fridge. He had heard about a tragic accident in which a family was killed by ammonia coolant leaking from their fridge. (ammonia was the only common refrigerant before Thomas Midgely took time off from developing leaded petrol to invent CFCs).

      So he invented a system with a metallic coolant that was completely sealed in a tube. It was moved through the tubes using a magnetic motor.

      Anyone know more? I'd love to know what the coolant could have been.

      Best wishes,
      Mike.

      • Einstein fridge [gtalumni.org]

        quick quote: It's basically an absorption-type refrigerator that uses ammonia, water and butane to create a chemical phenomenon that allows you to run the whole thing at a constant pressure, so you don't need moving parts like a pump or a compressor
    • Actually, no piping is necessary. A Stirling engine works by converting heat into mechanical energy, and is reversible. So the mechanical energy supplied by a power source is actually converted into the cooling effect.
    • You can also make refrigerators using a Stirling-engine like gas compression cycle

      Many thermoacoustic refrigerators are really variations on the Stirling engine that use standing pressure waves in place of the pistons (http://civil.colorado.edu/~muehleis/thermoacs/the rmoacs.html [colorado.edu], http://www.lanl.gov/mst/engine [lanl.gov]).

    • Back in yr 2k... (Score:3, Interesting)

      by Chembryl ( 596546 )
      I was asked to do some work on alternative methods of refridgeration by a very large alcoholic beverage company. The real pioneers of acoustic stirling heat engines are located here at Los Alamos [lanl.gov].

      Global Cooling [globalcooling.com]on the otherhand produce rival products to Medis El based on the Free piston Stirling Engine.

      Despite being some impressive technology, Free Piston Stirling Engines haven't really been taken up to well. Its a shame because they do seem to be much more efficient.

      If you are really interested then you might want to check this out At Ames Lab [ameslab.gov]. Gschneidner's work on the giant magnetocaloric effect is REALLY impressive. Its all about the exchange of entropy between magnetic and kinetic forms. Damn cool.

  • The technology isn't that new (Score:3, Interesting)

    by CodeShark ( 17400 ) <ellsworthpc@NOspAm.yahoo.com> on Wednesday December 04, 2002 @02:02PM (#4811472) Homepage
    I have been reading about sound-driven refrigerators in some of the electronics weeklies, etc. for more than a decade now, but it looks like the technology may be moving out of the lab into a prototype "consumer" unit.

    What I find more interesting than the projected "energy" savings (which I would have to see the science and the experimental data before I'd bank on), is that there is no compressor to wear out, no refrigerants, etc. Conceivably a service call would be something on the order of "open the sound box, unclip the sound driver, put in a new one", right?

    I wonder what the heat output on the hot side is -- enough to supply a home's hot water needs, perhaps?

  • Can I use it as a sub-woofer?

    Har, har.

    I've got nothing.


  • Err 1990 calling Slashdot. Its been well over a decade since CFC were used as coolants in refrigerators. Hell the US Goverment have replaced CFC/ODS from ICBMs as it says here [osd.mil] and other places.

    So while its cool the Ozone bit is already being dealt with.

    I still find it funny that something capable of killing millions of people is "Ozone friendly" apart of course from Ionising the atmosphere if it is used!
    • Decades, and they still 'brag' about not having CFC's on many products.
    • No, not CFCs - other greenhouse producing gases.

      CFCs were responsible for ozone depletion - that is different but related to the global warming problem. It is true that CFCs have been phased out, but other greenhouse gases are still in use.
  • Unfortunately, it was long ago (10+ years) back when I subscribed. Too bad they have no online archives I can search, or I'd give a link. The technology isn't really new, and makes a lot of sense, really (think what the compressor/condensor cycle does in traditional cooling, then think sound waves, think sonic booms, etc... lots of similarities there...).

    All in all, neat stuff, though.

  • Big deal... (Score:3, Funny)

    by Eric Damron ( 553630 ) on Wednesday December 04, 2002 @02:07PM (#4811520)
    "Refrigerators To Cool With Sound"

    So what. I live near the Capital of Washington State. We plan on heating our homes through the use of political speeches!
  • Cooling with sound waves? I'm pretty sure my Athlon Palomino system already does this... Otherwise it wouldn't be so friggin LOUD.
  • I have been waiting for this for ages. I first read the paper by Backhaus and Swift (and here [lanl.gov] is a more recent [lanl.gov] one) four years ago, and whichever site that directed my attention to that "promised" commercialization in the near future. Not exactly swift in high tech time, but still very much welcomed.

    Too bad I just bought a fridge for my dorm room. )=

    Werd
  • Just dig a holw a few feet deep in the ground, and get a cool 4deg all year round.

    Easy, didn't take any rocket science, doesn't produce green house gasses (maybe some radioactive ones), doesn't make any noise, doesn't cost much to run, only a space and a pick needed.
    • didn't take any rocket science, doesn't produce green house gasses, doesn't make any noise, doesn't cost much to run, ...doesn't work worth a darn anywhere useful.

      Assuming that 4deg is Celsius (Only a few places on Earth - mostly covered with ice - where that might be Fahrenheit), you're still talking about pretty high latitudes. 4C == 40F, but most temperate latitudes the constant ground temperature is more like 50F - 55F, getting warmer as you approach the tropics. Not cold enough for a fridge (typically 4C/40F), and you'd have to dig more than just "a few feet" anyway.

      Unless you live in Greenland.

    • At about 6' down the ground temperature is roughly equal to the average yearly temperature of your location. If that is 4 degrees where you live then you dont have much of a summer do you?

  • There hasn't been a DEPENDENCE on those gases... (Score:4, Insightful)

    by drinkypoo ( 153816 ) <drink@hyperlogos.org> on Wednesday December 04, 2002 @02:09PM (#4811539) Homepage Journal
    For a long time now. We've been able to use environmentally-friendly compounds in refrigeration for some time. In addition it is currently possible to build a refrigerator with no moving parts using peltier junctions which have come down in price dramatically since they first became popular, for obvious reasons. We currently only see this technology used in mobile coolers (coolers literally, with a 12V lighter plug) and in small refrigerators for RVs which have been heavily insulated to stop loss which will require additional power use.

    But it's possible to use ANY compressable gas for cooling. The ones we use now are simply very efficient because they can store a lot of heat. There are several ways to make a cooling system more efficient (at removing heat) assuming you have not already taken the particular step to the maximum.

    1. Add insulation. This is the most obvious. More efficient insulation means less heat loss. Of course it does raise the cost of opening the refrigerator door, in comparison to the cost ratio now. This does not completely absolve you from having quick cooling because of the resulting temperature variations.
    2. Move to a gas capable of storing more heat. This one's obvious. Of course we've gone in the opposite direction to get away from Freon. Not really a great solution unless we come up with something new.
    3. Run the system at a higher pressure. Requires a more powerful compressor, which in turn requires more energy put in at this stage. Also makes the system more dangerous as it is more likely to explode and more likely to be dangerous when it explodes. On the other hand if the gas is compressed farther it will be able to accept more heat, so you should be able to get a more rapid heat transfer, especially if you...
    4. Increase the quality of your heat exchanger. Maybe it's just larger, maybe you increase its outside surface area, maybe you increase its inside surface area, maybe you just make it bigger and thus (usually) heavier.
      Of course there are two heat exchange systems in a typical refrigerator; Those inside which are intended to absorb heat, and those outside which radiate it. In a peltier-cooled system the same heat exchanger(s) do both jobs. You also end up needing some kind of heat sink to increase surface area since the thermally active portions of peltier coolers are flat.

    By using some combination of these technologies we can move away from environmentally unsafe gases. While this new technology is certainly new and may be superior in many aspects, the only reason we have not moved to more efficient and/or "eco-friendly" designs to date is expense. Welcome to capitalist terra, my friends.

    • How about we use glass doors on our refrigerators, the kind that have two panes and a vacume betweem them. This way we wouldnt have to open the door so much. Duh!
    • Of course it does raise the cost of opening the refrigerator door, in comparison to the cost ratio now.


      You know what I want? A fridge built into my countertop that pneumatically raises up at the touch of a button, leaving all the cold air still down in the refrigeration pit. It'd work just like your adjustable office chair. Yes, I know it would be a pain to clean when your cat knocks half a jug of juice down there, but isn't that a price worth paying?


      Think about it... *whoooosh*... makes those 1950's techno-utopian dreams look almost attainable! ;D

      • That's just asking for it to break.

        I think the price of buying new lead-filled motors every year would offset any benefit of such a system.
    • "1. ...Of course it does raise the cost of opening the refrigerator door, in comparison to the cost ratio now. ..."

      Now we get to one of my pet peeves. Why doesn't any of the major, or minor for that matter, fridge manufactures make a chest style fridge. There are many chest style deep freezes, but no fridges. With a chest style fridge you'd only loose very little of the cold air in it when you opened it, rather than dumping darn near every bit of cold air out onto the floor as with the cabinet style fridges.

      Just my $0.02

      • Re:There hasn't been a DEPENDENCE on those gases.. (Score:5, Funny)

        by Tsar ( 536185 ) on Wednesday December 04, 2002 @03:22PM (#4812218) Homepage Journal
        Now we get to one of my pet peeves. Why doesn't any of the major, or minor for that matter, fridge manufactures make a chest style fridge.

        I don't understand your question. All refrigerators are chest style; they only set them on one end in the store so they'll occupy less space. Oh, wait--you aren't one of those idiots that installed it that way when you got it home, are you? Hahahahaha!!! How stupid can you get? I'll bet you put CD's in your PC's cupholder slot too, don't you?

        What a moron!
    • Move to a gas capable of storing more heat. This one's obvious. Of course we've gone in the opposite direction to get away from Freon. Not really a great solution unless we come up with something new.

      I believe the new gases (e.g. Puron) are more efficient at this than Freon. I have a new air conditioner that uses Puron. It runs considerably quieter and uses less electricity.

    • Re:There hasn't been a DEPENDENCE on those gases.. (Score:5, Insightful)

      by 5KVGhost ( 208137 ) on Wednesday December 04, 2002 @02:47PM (#4811892)
      By using some combination of these technologies we can move away from environmentally unsafe gases. While this new technology is certainly new and may be superior in many aspects, the only reason we have not moved to more efficient and/or "eco-friendly" designs to date is expense. Welcome to capitalist terra, my friends.

      It's not as though expense can be omitted from the equation entirely. Cheap and easily produced refrigeration technology (and air conditioning, which is closely related) have probably prevented more illnesses than any recent development since antibiotics.
      • Agreed. The most important developments in public health to date are:

        1. Refrigeration
        2. Sanitation (waste removal and treatment, including water waste)
        3. Water Treatment (You could say chlorination)
        4. Inoculation

        Certainly expensive refrigeration wouldn't solve problems for the impoverished. Of course lots of people in the world STILL don't have refrigeration, which (as anyone who has played civilization 2 knows) lets you produce more food because you can store/transport more.

        On the other hand for most of the world it makes sense to purchase initially expensive refrigeration hardware because it will save on costs in the long run. It regularly pisses me off that it is generally impossible to get a refrigerator with a basic set of features (IE, no ice maker/crusher, no water spigot, no computer in the door) without industrial-quality insulation.

    • On the other hand if the gas is compressed farther it will be able to accept more heat, so you should be able to get a more rapid heat transfer

      Sorry, it's been a few years since I had thermogoddamics, but I'm not sure this is correct. The heat transfer uses ENTHALPIC heat, which is given up or absorbed when the material changes state. In other words, Freon (ammonia, whatever) absorbs heat when it changes from a liquid to a gas, and vice versa. You compress the gas JUST ENOUGH to change its state to liquid, compressing it further has no effect (besides, compressing liquids isn't really practical anyway.) I believe what makes the Freon family so suitable for heat exchanging applications isn't it's enthalpic heat capacity, but the temperatures and pressures at which it changes state, i.e. practical in real-world terms. For example a compound that changed from gas to liquid at 2000 PSI at -140C wouldn't really be useful for much of anything. Some substances don't go through the liquid stage at all at practical pressures (carbon dioxide)... they go straight from gas to solid (and vice versa). Hard to pump a solid through a heat exchanger.

      Anyway, you made some great points, but the solutions may not be as practical or simple as you suggested.

      And I didn't see any mention in the article of what kind of compressed gas was used in the sound chamber.... Freon maybe? haha.

  • Though the BBC didn't get his name right (Garrett), I actually worked for his research lab at PSU. Very interesting stuff.

    There's more information about other projects the group is working on here [psu.edu].
  • CFCs are not the cause for global warming, they're the cause for the hole in the ozone layer.

    On the other hand, producing the sound waves will cost some electricity, the production of which is still mainly a main CO2 producer. So my idea is it will enhance the global warming, if anything.
  • It doesn't say how energy efficient these things are. The gasses in your refrigerator typically stay trapped in the plumbing for decades. The gasses released by the power plant that makes your electricity don't. If these things are less efficient than current refrigerators, they could actually be worse for the environment.

    Anybody out there know anything about the efficiency of this type of heat exchange?
  • The's a whole bunch of ways to cool things [slashdot.org]. It's just a matter of what works for a particular application.

    Thermo-acoustic cooling has been considered for use in space to reduce the weight and mechanical complexity of traditional refrigeration systems. [nasa.gov] iirc, there was also the advantage of using less dangerous/toxic gasses with acoustic cooling.
  • We know exactly whats happening with that, just like we did with the Ozone. Damn hippies. ;)

  • Alternatives (Score:3, Interesting)

    by Smidge204 ( 605297 ) on Wednesday December 04, 2002 @02:15PM (#4811616) Journal
    Global Cooling [globalcooling.com] has been developing more efficient (and safer) CFC-free refrigeration and cooling (even cryo-cooling) systems for quite awhile, now.

    =Smidge=

  • sonic fridge? (Score:3, Funny)

    by ocie ( 6659 ) on Wednesday December 04, 2002 @02:16PM (#4811628) Homepage
    BZZZZZZZZZZZZZZZZZ
    What did you say?
    BZZZZZZZZZZZZZZZZZ
    I asked if you'd like a cold beer.
    BZZZZZZZZZZZZZZZZZ

    Seriously though, I've seen a demo of this technology about 5-6 years ago and It's pretty cool.
  • From the article:
    "Prototypes of fully functioning acoustic fridges have already been built and one has even flown on the space shuttle."

    This is absolutely silly. Take your bucket of ice cream, tie a string to it, roll down the window, and let the vacum of space keep it chilled. To thaw iced-over items, rotate the shuttle to face the sun.

  • "Microwave" fridge (Score:4, Interesting)

    by CommieLib ( 468883 ) on Wednesday December 04, 2002 @02:19PM (#4811662) Homepage
    I wonder if this could lead to a sort of inverse microwave oven, i.e., one that could freeze water in under two minutes. Aside from having Margaritas muy rapido: it seems like rapid cooling could have:
    • medical applications
    • automotive applications (cool engine with sound generated by engine; kind of an sound based turbocharger)

    and obviously, chip cooling. I always thought loud music was cool.
  • "Dude! Turn up the beer cooler to 11!"

  • High-decibel sound (Score:5, Interesting)

    by silhouette ( 160305 ) on Wednesday December 04, 2002 @02:20PM (#4811678)
    At ridiculous volumes and/or frequencies, sound has some amazingly powerful properties, but I'm skeptical as to how practical such a technology can be. Here's why:

    A professor at my university was doing some personal research with a small team at his house on the properties of high-decibel sound. Based on incredibly complex differential equations, one could project two sound waves at ridiculously high frequencies and volumes to create a special kind of interference. This interference would in essence start a new sound (at a hearable frequency/volume) from where the two waves intersected, effectively making it seem like a controlled sound was being created out of thin air at any point in 3d-space.

    I don't think I need to point out applications to this technology. BUT - he decided to discontinue the project before it was ever completed. He had several pets in his house (dog + cats) that he tried to keep away from the testing, but they were still being driven crazy by the sound. He also started developing nasty headaches and suspected that his high-range hearing was being destroyed.

    Interestingly, one of the graduate students who worked with him on the project decided to continue the work on his own. From what I've heard, he had his work picked up and funded by the US military (DARPA, I think). When I heard this, it really didn't come as a surprise.
    • I can't recall what vehicle it was, but an experimental luxury car had two of these type of units integrated for the back seat. They were built into the headliner of the roof and (obviously) fired downwards, with the nifty effect of producing sound audible by the person below it but nowhere else. I'm not sure if it ever entered mass-production. At any rate, the theory was the same, where the interference between ultrasonic sound waves created an audible result. Aside from the aiming problems I believe the biggest issue was poor fidelity, as it was difficult to reproduce the full range of frequencies necessary for music with this technique.
    • say... wasn't this the story of a movie?

      something like the one with the space laser some
      college kids redirected to the professor's house
      and ended up destroying with popcorn?

      http://www.dvdmoviecentral.com/ReviewsText/real_ ge nius.htm
  • Los Alamos national lab currently holds the record on using thermal acoustic engine. The thermal efficient of their engine is about 30 percent, compare that to automobile engine. which is about 25 percent. http://www.lanl.gov/projects/thermoacoustics/TASHE .html [lanl.gov]
  • Well I'll just wait until it comes with Ogg Vorbis support before they get MY money!
    --
  • Sounds of 165 dB would cause a person's hair to catch fire from the frictional heating caused by air undergoing such intense compression and expansion.

    This is the coolest thing that I've read on /. in a long, long time.

  • Two piece refrigerator.. (Score:4, Interesting)

    by nolife ( 233813 ) on Wednesday December 04, 2002 @02:43PM (#4811845) Homepage Journal
    I've often wondered why a two piece conventional freon refrigerator never caught on. You could place the compressor, condenser, and the support structure outside the house connected with two hoses (same as your whole house AC). This would eliminate most of the internal noise and be far more efficient as you are not releasing the hot air from inside the fridge + the electrical and mechanical losses into the house. In the fall through spring season cycle it would even be more an advantage as it is often much cooler outside then in the house and the compressor could even be bypassed. This would allow for smaller, quiter, and higher efficiency refrigerators and allow more flexibility as you could replace the inside and outside units seperately when and if needed. The inital conversion would be a little higher because you'd have to run lines and a concrete pad or wall hanging device outside but long term it would be much less. Installation in new construction would be simple. Anyone have some VC money they want to get rid of?

  • In other news... (Score:5, Funny)

    by Anonvmous Coward ( 589068 ) on Wednesday December 04, 2002 @02:43PM (#4811855)
    ... refrigerator owners in Finland have been court ordered to pay royalties for the sounds generated by the space-age technology inside of their appliances. These royalties multiply depending on how many people are in the kitchen at the time. Hillary Rosen of the RIAA was quoted as saying "First they pirate our music, now they're cooling their food with it? Lots of people everywhere owe us money!"
  • use REALLY loud speakers.

    Then go to a lan party where you can frag your neighbor with 173 decibels. That would be coooooooool.

  • I Don't Get The Problem Here (Score:3, Informative)

    by Escape Tangent ( 594982 ) on Wednesday December 04, 2002 @02:44PM (#4811863) Homepage
    I feel compelled to lay to rest all of these posts about people going deaf from these refrigerators...

    Thankfully, even if the fridge cracks open the vast sounds generated within will not escape because the intense noise can only be generated in the pressurised gas locked inside the cooling system.

    Think about it for a moment. To generate the 120 dB in front of the speakers at a rock concert, you need some serious wattage. Those are powerful blasters, my friends. Also realize that the Decibel scale is logarithmic, meaning that the amount of "sonic energy" or volume -- whatever you want to call it -- between say 20 and 30 dB is a lot less than the amount between 120 and 130 dB. We're talking about a difference between 120 and 173 dB, which is, as the article points out, "tens of thousands of times more intense than any rock concert." I'm not a physicist or anything, but I'd assume that's why the sounds generated in the cooling unit work within a highly pressurized atmosphere -- so the sounds can (1) be created more efficiently and (2) carry through the gas properly. Open the unit into normal air and I don't believe it works anymore -- the atmosphere is too thin to produce those kinds of levels. On top of that, the unit is probably insulated in a vacuum anyhow, so as to prevent sound from escaping.
    You won't go deaf. Your animals won't go crazy. The most you'll probably ever hear is a soft hum.

  • Oh It Hurts! (Score:5, Funny)

    by NeuroManson ( 214835 ) on Wednesday December 04, 2002 @02:47PM (#4811894) Homepage
    "The research is being sponsored by ice cream makers Ben & Jerry's and Unilever. "

    "Humans feel pain when they hear sounds of 120 decibels, a level typically reached next to the speakers at a rock concert."

    So the purpose of this research is to improve on the ice cream headache? Why?

  • built one these in high school (Score:4, Informative)

    by xmldude ( 303952 ) on Wednesday December 04, 2002 @03:25PM (#4812256) Homepage
    A small team of 10 or so in conjunction with Lawrence Livermore National Laboratory built a thermo-acoustic refridgerator. It didn't work to well but it sure did make a hell of alot of noise. :)

    Our most successful aspect of the project was the prototyping of the stack. We discovered that a form of carbon areogel had some very cool properties that made isolating the heat exchanges easy. To test the new stack we created a "hooter-tube" (or holfer tube) which is the opposite of the refridgerator. We created a difference in temeperature to generate sound. We dipped one end of the tube in liqued nitrogen and then heated the other end with a blow dryer. It was a blast to play with becuase it was about the size of a light saber and becuase the open end was the cold end the air around the tip would condense and allow you to "see" the sound wave (well, a quarter of it anyway).

    here are some photos and other stuff:
    photo of hooter tube [navy.mil]
    photo of working refridgerator (very similar to ours) [navy.mil]
    Navy page with lots of info [navy.mil]

    BUNNY OF DEATH!

  • Hair Catching on Fire (Score:4, Funny)

    by serutan ( 259622 ) <snoopdoug@geekaz ... minus physicist> on Wednesday December 04, 2002 @03:46PM (#4812500) Homepage
    At last, a fridge that goes to ELEVEN.

  • Um... this is so like, 1993 (Score:4, Informative)

    by jonbrewer ( 11894 ) on Wednesday December 04, 2002 @04:17PM (#4812801) Homepage
    This research made some noise (ha!) about ten years ago. A company called Macrosonix [macrosonix.com] holds the patents. Even NPR [npr.org] has covered this in the past ten years.

    The best explanation of the technology I've seen is in "Fluid Power Journal [fluidpowerjournal.com]."

  • Smart assed comment... (Score:3, Funny)

    by frank_adrian314159 ( 469671 ) on Wednesday December 04, 2002 @04:32PM (#4812950) Homepage
    Sounds of 165 dB would cause a person's hair to catch fire...

    Marketing guy: Great! So we have Michael Jackson as a customer. Who else are we going to sell this thing to?

    **RIMSHOT**

    Thank you! Thank you! I'll be here all week!

  • Centralized Heat (Score:3, Interesting)

    by 3ryon ( 415000 ) on Wednesday December 04, 2002 @04:51PM (#4813214)
    What I would really like to see is a house designed around a centralized heat reservoir. Dump the heat generated by your Fridge and your AC into a stack where your water heater, your over, and your Heater can pull from. Obviously you'd also want a heating element there, but the energy savings of recouping the heat from the other applicances would be significant.

  • I remember seeing this 10 years ago... (Score:3, Interesting)

    by kakos ( 610660 ) on Wednesday December 04, 2002 @04:54PM (#4813246)
    I can't remember the name of the program, but it was one of those "Look what's new in science" type programs on the Discovery Channel. On this one I remember, I saw them talking about a sonic fridge. This was 10 years ago. They had a prototype 10 years ago. What happened to that?

  • Updated prank call.... (Score:4, Funny)

    by shpedoikal ( 631433 ) on Wednesday December 04, 2002 @04:56PM (#4813265)
    *ring* *ring*

    HELLO?

    Is your refrigerator running?

    WHAT?!?

    Is your refrigerator running?

    WHAT?!? YOU'LL HAVE TO SPEAK UP!

    Oh nevermind.. *click*

  • Ogg. (Score:3, Funny)

    by Eric_Cartman_South_P ( 594330 ) on Wednesday December 04, 2002 @05:18PM (#4813506)
    I don't care how cool or loud it is... if it doesn't support Ogg I'm not getting one.

  • Finally, a use for my neighbour's daughter (Score:3, Funny)

    by TekPolitik ( 147802 ) on Wednesday December 04, 2002 @07:19PM (#4814640) Journal
    The article claims that 165dB is sufficient to cool a refrigerator - my neighbour's daughter exceeds that by a long shot. Does this mean we can put her inside a tube and get her to keep my beer cold?

  • Sounds promising, but.. (Score:3, Insightful)

    by salimma ( 115327 ) on Wednesday December 04, 2002 @09:45PM (#4815548) Homepage Journal
    .. bear in mind one thing: cost. Obviously any innovative solution that is ecologically sound is good and all, but the worry is that the uptake in 3rd world countries would be slow.

    The new fridge might be more reliable and does not pollute, but the old technology has an army of technicians who can service it, and I believe countries like China are still allowed to produce CFC coolants. In fact, when countries agreed to phase out CFC, China's phase-out was based on its production several years in the future, and as a result its production actually jump in the subsequent years as manufacturers took advantage of the loophole.

    More information here [unep.org]

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