Sounds as fire extinguishers

[Lee in Montreal]

Interesting

http://www.wptv.com/news/local-news/...xtinguish-fire

"Viet Tran and Seth Robertson's new fire extinguisher looks a little like a conventional one, but instead of a compressed air tank spewing out chemicals, theirs has a loudspeaker the size of subwoofer drumming out sound waves."

[Allanvh5150]

So someone has invented something that everyone has known about for 40 years or so. Interesting.

[Ruediger]

Sound: molecules are stationary, vibrate back and forth but do not move. Wind: molecules travel.

When you blow out a candle, you apply wind, not sound. You blow away the zone of reaction (the flame) from its supply (the wick), and you cool the gas escaping from the wick, so that it doesn't have the required temperature.

That strange device cannot produce any bass. It's like an open baffle loudspeaker. The sound from the rear of the driver and the sound escaping at the front will short-circuit.

I think it's a joke, maybe they are using a fan in the device.

Ruediger

[hjames]

I dunno - its the local college - seems like a lot of publicity over it.

https://newsdesk.gmu.edu/2015/02/pum...-fights-fires/

From the look of it, there is a driver on the back of a tube.
The tube has a baffle on the front with a smaller hole -
so it focuses the air/sound in the wide tube into a reduced column, increasing the airspeed.

Kind of like the kids' toy "wind gun"




http://www.extremetech.com/extreme/1...e-extinguisher

[Hoerninger]

Place a candle in front of a woofer, best with a steady deep tone - you will see.
__________
Peter

[Ruediger]

Place a candle in front of a woofer, best with a steady deep tone - you will see.
__________
Peter

When you do this, does the woofer make large excursions ("pump"), or does it hardly move? In the 1st case, the woofer "makes wind", it does not radiate efficiently. In the 2nd case it generates sound.

Ruediger

[hjames]

Doesn't seem like a difficult concept to prove to yourself -
https://newsdesk.gmu.edu/2015/02/pump-bass-douse-blaze-new-mason-invention-fights-fires/

Screen caps show the concept pretty well ...
Looks like maybe a 12 inch woofer on a matched diameter Sonotube -

In the bottom picture you can see how the output is choked down
by the hole on the baffleboard. Maybe 1/3 the diameter of the tube.

Think of the wind motion with the bass port on a big subwoofer,
or one of those bazooka subs for car use ...

Here are some of the prototype versions


And this is the one they did the YouTube video demo with

[Hoerninger]

@ Ruediger:
50 Hz with a 13 cm/ 5 inch speaker works fine.
(Rayleighscher Strahlungsdruck/ radiation pressure)
__________
Peter

[Allanvh5150]

I would think any of these would be a better idea.

http://forsythfirerescue.org/fire-sa...extinguishers/

Allan.

[ivica]

Doesn't seem like a difficult concept to prove to yourself -
https://newsdesk.gmu.edu/2015/02/pump-bass-douse-blaze-new-mason-invention-fights-fires/

In the bottom picture you can see how the output is choked down
by the hole on the baffleboard. Maybe 1/3 the diameter of the tube.

Hi

It seems to me that the hole diameter is about 1/2 of the tube diameter, but in that situation the area of the hole is 1/4 of the driver cone surface.

regards
ivica

[Horn Fanatic]

Sound: molecules are stationary, vibrate back and forth but do not move. Wind: molecules travel.

When you blow out a candle, you apply wind, not sound. You blow away the zone of reaction (the flame) from its supply (the wick), and you cool the gas escaping from the wick, so that it doesn't have the required temperature.

That strange device cannot produce any bass. It's like an open baffle loudspeaker. The sound from the rear of the driver and the sound escaping at the front will short-circuit.

I think it's a joke, maybe they are using a fan in the device.

Ruediger

Thank you for pointing that out. There isn't a snow ball's chance in Hell that device could be "scaled up" to fight forest fires, as the MIT students claim. They're selling snake oil. The cylinder on the front appears to be nothing but a simple acoustical low-pass filter. The red cone is visible at one angle, revealing there is nothing going on structurally inside the tube. The device is simultaneously drawing the air away from the flame and blowing on it, therefore, all the device is doing is disturbing the source of air to the flame. You'll notice in the video how close he needs to place the device next to the flame?

[Hoerninger]

Although I'd prefer to go with Allanvh5150 look here:


__________
Peter

[Hoerninger]

For those who can't perform themselves:

to the left there is no sound.
To the right there is a little 4 Ohms box with a 5 inch speaker plugged to a 50 Hz transformer with 12 volts (about 36 watts). The candle is placed close to the speaker, the flame does not flicker.


___________
Peter

[Allanvh5150]

The good old vortex cannon

https://www.youtube.com/watch?v=IyAyd4WnvhU

Allan.