Engineering students use sound waves to put out fires

Engineering students use sound waves to put out fires

Two engineering students at George Mason University have found a way to use sound waves to quash fires and have built a type of extinguisher using what they have learned that they hope will revolutionize fire fighting technology. Viet Tran a computer engineering major and Seth Robertson, an electrical engineering major, chose to investigate the possibility of using sound to put out fires as a senior research project and now believe they have found something that might really work.

Prior research has shown that can impact fires, and other researchers, such as those working for DARPA a couple of years ago, even investigated the possibility of using sound to put out fires, but thus far, no sound based extinguishers have been built and sold as a means to stop fires. The research by the duo at GMU might change that.

As the two students told members of the press, they started with the simple idea that sound waves are also mechanical or (due to the back and forth motion of the medium in which they pass through), which can cause an impact on objects. In this case, on the material that is burning and the oxygen around it—if the two are separated by such waves, they reasoned, the fire would have to go out. They took the trial-and error approach, aiming speakers at small fires and sending out different types of sound at different frequencies. Ultra-high frequencies did not have much impact, they noted, so they tried going low—in the 30 to 60 Hertz range, and found that it did indeed cause fires to go out.

Encouraged, they took the idea further by building a portable device capable of focusing the pressure waves directly at a fire. In essence, it is composed of an amplifier, a power source and a collimator made out of cardboard tube (for focusing the waves). The result is a reasonably small extinguisher that works without the use of water or chemicals. Their initial impulse was to use the extinguisher for small fires in the kitchen, but now believe it may have a far wider use.

The fire extinguisher uses low-frequency sound waves to douse a blaze. Engineering seniors Viet Tran and Seth Robertson now hold a preliminary patent application for their potentially revolutionizing device.

The two students acknowledge that there is still a lot of work to do before they will know if their extinguisher might be useful for fighting real fires—thus far, it has only been tested on small alcohol flames. At issue is whether it can be used on bigger fires, and because it does not have a coolant, whether fires that go out, because the material will still be hot, will reignite once the sound waves cease.

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Mar 26, 2015
While this is fun to watch, it is fairly simple. All they did was connect a power supply to an amplifier, connect that to a woofer, and build a chamber to focus the air from the woofer output in one direction, with a limited range. My ported subwoofer in my car will put a lighter out, basically the same thing. This sounds high tech, but in reality they are just creating enough air turbulence to extinguish the fire. I don't think there is any real scalability to this idea.

Mar 26, 2015
Agreed, all it would do in a chip pan fat fire is blow the flaming chip fat all over the place

Mar 26, 2015
This shows imagination. It might come to something; it's worth looking. Five stars from me, just for trying. It's too easy to miss something because you KNOW it can't possibly work.

Mar 26, 2015
This sounds high tech, but in reality they are just creating enough air turbulence to extinguish the fire. I don't think there is any real scalability to this idea.

They are basically creating a vortex gun which yes is not very scalable at a distance which is why they mention drones.
However.. there are other applications that have been refined for using sound for offensive purposes that could be manipulated to apply for these purposes as well such as.. google up the "lrad sound cannon"

Mar 26, 2015
Oh, don't get me wrong, I think it is cool as hell! I just don't think fighting fires with it is practical. Most fires are not easily "blown out", because as long as the heat, fuel and oxygen are still present, a temporary loss of flame will not stop combustion. Sure you can stop gases and liquids from burning this way, a solid material burning can re-ignite.

I think finding a safe way to remove oxygen from the immediate vicinity of a fire would be the best, much like Halon fire extinguishers. Unfortunately humans need oxygen as well, so it works best when humans are not in the equation.

Mar 26, 2015
These ideas come in press each year - but I never saw any practical output from it.

Mar 26, 2015
So, what else can it put out? Maybe your ears?

Mar 26, 2015
Recently there was an article about heat and sound both being transmitted as subatomic particles and that theoretically they are the same particle, there may be more sense here than is obvious

Mar 26, 2015
Could be handy in riots etc when 'water cannon' are politically unacceptable, EFR fire-fighters dare not approach and the 'usual suspects' are throwing fire-bombs at the police cordon.

Snuffing such weapons, even for a few seconds at a time, would be so beneficial...

Mar 26, 2015
This might be useful for spacecraft or high-altitude aircraft or submarines, where it is hazardous to use chemicals because you will contaminate your supply of air.

This could also be useful for mines or any other place where ventilating chemicals is problematic.

Mar 27, 2015
Silly kids.. If it was blown out, the liquid would be all over the sidewalk. The flames would have shot out to the rear of the pan. The fire was separated from the source long enough to extinguish it using the large sine waves from low hertz. What it won't do is put out forest fires or anything that has a burning ember. It will just reignite. Just mix the two together sound and water. Would allow fireman to get closer to the source faster.

Mar 27, 2015
Nice idea, but similar to using dynamite to extinguish oil well fires, but on a smaller scale. Don't you think? What would be absolutely amazing is if it they could tweak it to work on trees. Doubtful, but it would be a welcome surprise.

Mar 27, 2015
This might be useful for spacecraft or high-altitude aircraft or submarines, where it is hazardous to use chemicals because you will contaminate your supply of air.

This could also be useful for mines or any other place where ventilating chemicals is problematic.
@Ensign_nemo
before that, they will have to do extensive testing to insure that structures can withstand the use... it would be bad to use this underground if it causes structural instability... don't know how it would do in a pressurized cylinder either

interesting device... will continue to watch this develop
looks effective on kitchen type grease/accelerant fires...
would like to know more and see how it does with other stuff... like wood fires.
how much does it penetrate?

it definitely doesn't seem to be helping with sound pollution, though

Mar 27, 2015
In that video, they appear to put a fairly tiny amount of flammable liquid in that pan and then extinguish it using their sound wave generator at fairly close range. That is interesting, but of fairly limited utility; they seem to recognize this, given their comments that their current "vision" is to use it for putting out stove-top fires. I suspect they realize that it would not be particularly effective in putting out anything where hot embers remain to pose a reignition risk. In that case, it might still work, if it could be left in place and operational as a "flame suppressor", until the embers cooled below the reignition temp.

It should also be noted that this doesn't work by "blowing out" the flames in the same sense that a continuous stream of air would. It works by inducing local turbulence that destabilizes the temp and gas composition gradients that the flame requires to stay lit. Scalability will likely be an issue, as already pointed out by others.

Mar 29, 2015
What is important is that these guys have the patent in their pocket for making a fire extinguisher using sound. They will make millions. It doesn't matter how simple the idea is. Simple physics applications is what complex gadgets are made up of.


Mar 30, 2015
The implication in some of the comments that the fire is blown out is wrong. The action of the low frequency oscillations of the air near to the fire is to overcome the rate at which oxygen and the vapor from the hot (carbon-like) material can combine and burn. Once the heat is eliminated these materials will not burn spontaneously, but this stage is not so easy to reach and must be achieved first.

Mar 30, 2015
In that video, they appear to put a fairly tiny amount of flammable liquid in that pan and then extinguish it using their sound wave generator at fairly close range. That is interesting, but of fairly limited utility

It's a low tech demonstration prototype. Think about what could be done with an annular array like in ultrasonic imaging - where you can set the depth of focus depending on how you actuate the array (or a metamaterial approach for focussing the sound beams).

There are already anti-citizen (erm...anti-riot) weapons based on similar designs that can project significant sonic energies over largish distances.

Alternatively couple this with drones which can get close (but cannot carry huge amounts of water) and you might get a system that's worth employing. Especially in situations where energy is available, but water is not (e.g. forest fires)

Mar 30, 2015
I could stoke a fire with that pretty well.

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