It may sound far-fetched but one day sound may be the method of choice for putting out fires.
A recent feature on BBC’s The One Show programme demonstrated how certain low frequency sound waves can be used to extinguish flames. The clip featured a large sound system that produced low pitched bass notes. The idea was that the sound from the speakers would be used to put out the candles on a birthday cake.
When the sound was played, it took a few seconds but eventually the flames began to flicker and then went out completely. This proved the theory that sound waves could be effective as a new approach to firefighting, although it’s still early days.
There are safety concerns with this method, as at this frequency sound is more felt than heard and may pose a potential risk to health, particularly if people are exposed to it over a long period of time.
How sound waves extinguish flames
The US Defence Advanced Research Projects Agency (DARPA) has been investigating the potential of sound waves to fight fires. In a video issued by them, after fewer than 10 seconds of being exposed to a low frequency sound you can clearly see the flame is extinguished.
How this works is that the sound waves disrupt the flame by increasing air speed and thinning the layer where combustion occurs. The acoustics also disturb the surface of fuel, increasing vaporisation resulting in the flame widening and temperatures inside the flame cooling.
Cooling the temperature of a flame removes heat, which is one of the essential elements that keep a fire burning. Without heat present a fire will go out. This factor is used by water based fire extinguishers which put out fires by cooling them down.
It may take some time to find a practical way to use this effect and turn it into an effective alternative to current fire extinguishers, but the research is looking promising.
So who knows… perhaps in a few years from now, sound fire extinguishers will be the next big thing.
You heard it here first…Tags: fire extinguishers, new fire fighting technology, putting out fires, the one show