I remember reading about all chicken at a poultry farm being violently sick/dying for apparently no reason. It turned out the culprit was machinery at a nearby factory that emitted sound at a frequency equivalent to the resonant frequency for brain cavity of the chicken.

  • Could the story be true?
  • Could sound be used to purify water of bacteria/viruses (preferably filter, else cull)?
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    $\begingroup$ I wonder if at least the first part of this question might be better treated at Skeptics... $\endgroup$ – David Z Oct 2 '11 at 19:15
  • $\begingroup$ Erm. For what it's worth this was probably in a programming magazine I read ( easily 15 years ago that I read it. Think it was 7 or 8Hz that caused the death of the chicken ) $\endgroup$ – Everyone Oct 2 '11 at 19:18
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    $\begingroup$ I'm not comfortable enough to make it an answer, but I think you might be on to something. I remember a professor once telling me that part of the damage of an explosion (other than shrapnel) is the huge amplitude of the sound wave causing a damaging pressure differential; this is the effect that blows out eardrums for example. If you could match the wavelength to the scale of the bacteria and then crank up the amplitude, you might be able to kill something with it. $\endgroup$ – AdamRedwine Oct 3 '11 at 12:55
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    $\begingroup$ Pressure differentials really wreak havoc on discontinuities such as gas bubbles in liquids, or the gas on either side of your eardrum. Bacteria don't have gas bubbles inside them. On the filtering part, you'd have to consider impure water a colloid. Vibration (sound) can accelerate the settling of flocs. See e.g. en.wikipedia.org/wiki/Colloids#Colloids_in_the_environment $\endgroup$ – MSalters Oct 3 '11 at 14:17
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    $\begingroup$ Ultrasound is routinely used in biology labs to disrupt cell membranes. Doubtful whether it would do much to viruses. $\endgroup$ – user2963 Oct 3 '11 at 14:29

The major problem with ultrasound as a mechanism of purification is that it doesn't break molecules. Heat at least denatures proteins and breaks hydrogen bonds, but ultrasound is of a just smaller order of magnitude of energy at the atomic scale, which can be of the order of the adhesive forces holding the liquid together, but not of stronger molecular bonds.

But I think you can do it a different way: use a sound waves intensity gradient to move the biological impurities in the water to a part of the container, by having them walk down an effective potential gradient, like optical tweezers move molecules. This requires only that the density/stiffness of the molecules be different from water, so that the sound energy at a given mode is different inside the molecules than in the water. If it is greater, the molecule will move to the regions of greater intensity. If it is less, it will move towards the regions of smaller intensity. By arranging the sound wave to have an intensity gradient, you can make all the molecules segregate towards/away from the microphone, leaving water in the middle with only ionic or small molecule impurities, which are not affected by the sound.

You can flush the sides away, and repeat to make a purer water. This might work for getting rid of prions, which aren't disinfected by boiling.

This article is the only thing I found that might be relevant, but it is paywalled:

I think this might be a very useful idea.

  • $\begingroup$ Wrong, Ron! Ultrasound of sufficient intensity creates microscopic bubbles which, on collapse, give rise to similar things as cavitation does, but much stronger in the small jets. Sonoluminiscense and extremely high temperatures for very short time occures (evidence by chemical reactions). Why is it not used to desinfect? Either it is not practical, or all the medicine people missed something big. Knowing how many thousands of ultrasonic cleaning baths linger around in labs since the 50ties, I think th first thing is true. $\endgroup$ – Georg Oct 4 '11 at 18:37
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    $\begingroup$ @Georg: Not wrong. The microscopic bubbles are irrelevant for the discussion, except that they demonstrate that the ultrasound energy can be of the same order as the cohesion force. The ultrasound will not disinfect by itself, of course, but if you set up a narrow line sound-generator and pump some watts through the water for a while, you should get segregation of biological impurities near and away from the microphone, depending on the details. The middle region can then be impurity free. Why have people missed this? Somebody always has to be the first to suggest it. $\endgroup$ – Ron Maimon Oct 5 '11 at 0:16
  • $\begingroup$ Cohesion? I gave You some hint: Sonolumuniscense $\endgroup$ – Georg Oct 5 '11 at 4:28
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    $\begingroup$ @Georg: Why are you speaking in riddles? Sonoluminscense is failure of cohesion, followed by bubble collapse. $\endgroup$ – Ron Maimon Oct 5 '11 at 5:11
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    $\begingroup$ Ron, there is an "unwalled" version, see here scholar.google.com/… $\endgroup$ – Yrogirg Aug 13 '12 at 5:58

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