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Posibility of sound to put off fire.

  1. Mar 22, 2012 #1
    Hi all
    i am now prepar to write a essay about use sound to put off fire, and the pre-reserach i have done have show that the sound do can put off fire, however the very low efficient. What i want to find out how can i extend its distance to put out fire, i have try something ,and some of them works and some do not. i tried to use a tube which is filled with water, however it does not work at all, however when i used a hollow tube, and put it in the speaker, it do extend the distance. is there any other ideal to extend the distance????
     
  2. jcsd
  3. Mar 22, 2012 #2
    Yea a Fan would, and it makes sound.

    lol, sound putting out fire. Oh like a fire alarm. I see now. :wink:
     
  4. Mar 22, 2012 #3
    Fires started by thermal radiation from nuclear explosions can be extinguished by blast waves. See http://glasstone.blogspot.com/2006/04/ignition-of-fires-by-thermal-radiation.html

    "......Thomas Goodale's report Effects of Air Blast on Urban Fires, URS Research Company, California, report URS 7009-14, also AD723429, December 1970, showed that where thermal radiation from a simulated 1 megaton burst ignites curtains and papers, the blast wave arrived and blew fires out. At 1 psi, 50% of burning curtains are extinguished by the blast wave, burning fragments from the remainder can be blown into the room by a peak overpressure of 1 psi. But in all case above 2.5 psi peak overpressure, 100% of incipient fires were extinguished by the blast wave, unless the whole room was filled with tindering like newspaper trash and directly facing the fireball so as to suffer immediate 'flashover' like the trash filled room exposed to ENCORE.

    Blast winds displace flames and cool the burning material to temperatures below those needed for ignition, thus extinguishing fires. Burning beds, all curtains and upholstered furniture are only extinguished by peak overpressures of 2.5 psi and higher. The beds and upholstered furniture may then continue to smoulder, and can rekindle into fires after 15 minutes or more. During this time it is very easy to stamp out the potential fires......"


    I think this effect was actually seen at the Nevada Test Site.
     
  5. Mar 22, 2012 #4

    berkeman

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    Staff: Mentor

    Are you familiar with the "Fire Triangle"? What are the 3 elements needed for fire to exist?

    And how do you propose to interfere with one or more of those 3 elements by using sound?
     
  6. Mar 22, 2012 #5
    Well.... actually, i tried this one, when i set the frquency as 50Hz the flame viberate a lot, and when i set the frequency as 25Hz the fire was off suddenly. i think the ideal would casue this happen is because the when the sound wave generated, it caused the butane to butane to viberate, and when the butane is viberate fast enough, and the butane can not recat with oxgen enought. And, as a result, the fire was off.
     
  7. Mar 22, 2012 #6
    Thanks for the article.
     
    Last edited by a moderator: Mar 23, 2012
  8. Mar 23, 2012 #7

    Bobbywhy

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    Gold Member

    Fighting Fire with Sound
    Acoustic Waves Could Help Put Out Flames in Zero-Gravity Environments
    October 1, 2006
    Aboard NASA's "Weightless Wonder" airplane, physicists are experimenting with combustion and fluid flows in zero-g and developing a fire extinguishing system based on sound waves. The technique could be use to put out fires on the International Space Station and the Space Shuttle.
    One team’s results: The team uses(d) a candle and speakers to try and prove a theory that sound can cause pressure around a flame to drop, forcing it to go out.
    There are some ups and downs with all the science projects ... And although the team didn't prove the sound wave theory in zero gravity here, they've shown that sound can extinguish small flames in their lab.
    http://www.aip.org/dbis/stories/2006/15224_full.html [Broken]

    A good introduction to the process:
    http://www.scientificamerican.com/article.cfm?id=when-fire-strikes-stop-drop-and-sing

    Maybe useful for your demonstration to visualize the pressure waves:
    “Visualizing the sound field of an acoustic fire extinguisher” at: http://adsabs.harvard.edu/abs/2006APS..MARB42003P

    From here on Physics Forums in February, 2007:
    Notice that the thread starts out discussing extinguishing fire with acoustic pressure waves, and then degenerates into a discussion of putting out flames from a distance using vortex rings (smoke rings)…quite a different process.

    Sound vs. Fire - need help

    https://www.physicsforums.com/archive/index.php/t-155184.html [Broken]
     
    Last edited by a moderator: May 5, 2017
  9. Mar 23, 2012 #8
    It is common practice to put out oil well fires by using dynamite. See

    http://en.wikipedia.org/wiki/Oil_well_fire

    The common lore is that the dynamite blast "removes all the oxygen necessary for the fire to burn". Dynamite includes all it own oxidant, so it cannot consume the oxygen in the air. The pressure shock wave from the explosion does not remove the oxygen from the air, but does create a wind. So how does dynamite extinguish a wellhead fire? Does it smother the fire with the combustion products of the dynamite explosion itself? A very high wind can blow out a wellhead fire, just like blowing out a candle flame. An acoustic (sound) wave cannot smother a flame, unless the flame is smothered by its own combustion products.
     
  10. Mar 24, 2012 #9

    Bobbywhy

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    Gold Member

    Fire suppression using acoustics is quite different from using blast waves. Here are a few more references you may use to extinguish fires using sound.

    “The parametric array is a nonlinear transduction mechanism that generates narrow, nearly sidelobe free beams of low frequency sound, through the mixing and interaction of high frequency sound waves, effectively overcoming the diffraction limit (a kind of spatial 'uncertainty principle') associated with linear acoustics. Parametric arrays can be formed in water, air, and earth materials/rock.”
    http://en.wikipedia.org/wiki/Parametric_array

    “Researchers since the early 1960s have been experimenting with creating directive low-frequency sound from nonlinear interaction of an aimed beam of ultrasound waves produced by a parametric array using heterodyning. Ultrasound has wavelengths much smaller than audible sound and thus can be aimed in a much tighter narrow beam than any traditional audible loudspeaker system.”
    http://en.wikipedia.org/wiki/Sound_from_ultrasound

    Here are a few technical papers you may find useful:

    F. J. Pompei, "The use of airborne ultrasonics for generating audible
    sound beams," Journal of The Audio Engineering Society, vol. 47, pp.
    726-731, Sep 1999.

    M. Yoneyama, J.-i. Fujimoto, Y. Kawamo, and S. Sasabe, "The audio
    spotlight: An application of nonlinear interaction of sound waves to a
    new type of loudspeaker design," The Journal of the Acoustical Society
    of America, vol. 73, pp. 1532-1536, 1983.

    M. B. Bennett and D. T. Blackstock, "Parametric array in air," The
    Journal of the Acoustical Society of America, vol. 57, pp. 562-568,
    1975.

    T. D. Kite, J. T. Post, and M. F. Hamilton, "Parametric array in air:
    Distortion reduction by preprocessing," The Journal of the Acoustical
    Society of America, vol. 103, pp. 2871-2871, 1998.
     
  11. May 31, 2013 #10
    Why is SideLobe reduction important for signals

    why must signals be as sidelobe free as possible?
    I notice that this is the aim of compressing chirp waveforms used for telecommunications like in sensing applications. This is done via "windowing", a process that I am also not clear about, except that it means filtering via a LPF.
     
  12. May 31, 2013 #11

    Bobbywhy

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    Gold Member

    Since you asked last year about "use sound to put off fire" the ideas contained in the references described methods to direct the maximum amount of acoustic energy onto the fire using parametric arrays. This is accomplished by "beamforming". This results in most of the energy being concentrated in a small volume, with the minimum amount in sidelobes.

    Here are two more references to assist you:

    The power density in the side lobes is generally much less than that in the main beam. It is generally desirable to minimize the sidelobe level (SLL), which is measured in decibels relative to the peak of the main beam. The main lobe and side lobes occur for both conditions of transmit, and for receive. The concepts of main and side lobes, radiation pattern, aperture shapes, and aperture weighting, apply to optics (another branch of electromagnetics) and in acoustics fields such as loudspeaker and sonar design, as well as antenna design.
    http://en.wikipedia.org/wiki/Side_lobe

    Apparatus for reduction of side lobes in a beam pattern of an array
    http://www.google.com/patents?hl=en...age&q=acoustic beam pattern sidelobes&f=false
     
  13. May 31, 2013 #12
    Woah, ok got it thanks! (although actually i did not ask the original question a year ago)
     
  14. May 31, 2013 #13

    olivermsun

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    Science Advisor

    Out of curiosity, what is the difference in physical principle between (using) a "blast wave" and using an "acoustic wave"?
     
  15. May 31, 2013 #14

    Bobbywhy

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    Gold Member

    As often happens when using the English language in scientific studies different terms may be used by various groups to describe the same phenomena. For instance, the term “blast wave” is defined clearly in this Wiki entry:
    http://en.wikipedia.org/wiki/Blast_wave

    Now, have a look at this:
    http://en.wikipedia.org/wiki/Shock_wave

    And then, this:
    http://en.wikibooks.org/wiki/Engineering_Acoustics/Detonation

    Therefore, one might conclude that the terms “blast wave”, “shock wave”, and “detonation wave” could be used interchangeably. Since I am not qualified to make such a determination, I leave it to others to decide.

    As for your specific question, the differences between using a “blast wave” and sound waves for fire suppression are clear. Blast waves:

    “Oil well fires are more difficult to extinguish than regular fires due to the enormous fuel supply for the fire. In fighting a fire at a wellhead, typically high explosives, such as dynamite, are used to create a shockwave that pushes the burning fuel and local atmospheric oxygen away from the well.(where the flame develops) (This is a similar principle to blowing out a candle.) The flame is removed and the fuel can continue to spill out without catching on fire.”
    http://en.wikipedia.org/wiki/Oil_well_fire

    Now, as for using sound to suppress fire:

    “Citing a lack of innovation in fire-extinguishing methods over the last 50 years, the Defense Advanced Research Projects Agency (DARPA) last week revealed an ear-buzzing new method for putting out fires: blast it with fine-tuned frequencies. Officially referred to as "acoustic suppression of flame," this simple yet potentially revolutionary method simply relies on two speakers playing a specific low frequency toward the fire. The resulting acoustics increase air velocity, making it easier to alter the origin of the fire's combustion, also known as the flame boundary layer. A DARPA statement says the specific sound "leads to higher fuel vaporization, which widens the flame, but also drops the overall flame temperature. Combustion is disrupted as the same amount of heat is spread over a larger area."
    http://news.cnet.com/8301-17938_105-57473335-1/darpa-drops-the-bass-to-extinguish-fire/

    Here is a more detailed description of the technique:

    “Performers also evaluated the use of acoustic fields to suppress flames. In the video below, a flame is extinguished by an acoustic field generated by speakers on either side of the pool of fuel. Two dynamics are at play in this approach. First, the acoustic field increases the air velocity. As the velocity goes up, the flame boundary layer, where combustion occurs, thins, making it easier to disrupt the flame. Second, by disturbing the pool surface, the acoustic field leads to higher fuel vaporization, which widens the flame, but also drops the overall flame temperature. Combustion is disrupted as the same amount of heat is spread over a larger area. Essentially, in this demonstration the performers used speakers to blast sound at specific frequencies that extinguish the flame.”
    http://www.darpa.mil/NewsEvents/Releases/2012/07/12.aspx

    Although the two mechanisms of fire suppression seem similar, there is one major difference: during the “blast wave” scenario only one overpressure/under pressure pulse interacts with the fire, whereas when the low frequency acoustic field is applied a continuous succession of pressure/rarefaction pressure waves interact with the fire.
     
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