Sound waves as fire extiguisher?

A very interesting article about the interaction of sound and fire (candle flame). A video of the experiment can be found here.
Mythbusters also seem to have explored the same: http://mythbustersresults.com/episode76



From the article:
"In 2004 Dmitriy Plaks and several of his fellow students at the University of West Georgia tested whether sound waves can douse fires in hopes of using sound to extinguish flames in a spacecraft. They placed a candle in a large topless chamber with three bass speakers attached to the walls. The candle was lit and the Canadian rock band Nickelback's "How you remind me" was pumped through the subwoofers. Within roughly 10 seconds, once the song hit a low note, the flame was out, according to results published in 2005 in The Journal of the Acoustical Society of America.

"We don't know exactly what's going on," Plaks says, now a student at the Georgia Institute of Technology.

Physicist James Espinosa at Rhodes College in Memphis, Tenn., a former advisor to the student team, notes that the candle wasn't running out of oxygen to fuel the flame because the chamber was large and open to the air. He also doesn't believe that wind—which would actually displace the warm air around the candle with cooler air—had put out the fire, although only high-resolution thermal images would have been able to verify that.

There is another indication that the fire hadn't been extinguished by wind: frequency (the time it takes for succeeding peaks of a sound wave to pass a fixed point). "There's some special frequency at which a candle flame extinguishes," Espinosa notes. The students tested a range of frequencies from five to several hundred hertz. They found that the effective range was between 40 and 50 hertz, within the range of human hearing."

My guess that it has to do something with resonance of the sound waves. Maybe we should equip our firetrucks with large speakers blaring music or sound at different frequencies. This should speed up the process of containing fires.

Genuinely 'authentic'

Sunset

Human Tetris

So much for security of checked-in baggage

Read this funny story from a air traveller. It also raises a few questions regarding security. Source of the story: http://www.elliott.org/first-person/round-trip-on-the-conveyor-belt/

Round trip on the conveyor belt

In North American airports, there are warnings posted above the luggage carousels: “Please don’t step on the conveyor belt.” These signs are often missing when you travel internationally, and I recently discovered why.

Two years ago, I was in China with a friend who is a professor at the University of Texas medical school, and a group of his students. We had traveled from the old capital of Xian, westward through the oasis towns and deserts of central China, ending up in the 2,000-year-old Uighur city of Kashgar, near the Afghanistan border.

At a sprawling bazaar known locally as the Camel Market, I picked up several small handmade Uighur knives as gifts. Instead of packing them into my checked-in luggage, I slipped them into my carry-on bag by mistake.

We flew out of Kashgar the next day from an incongruously modern airport recently built to open up this very remote part of China to trade and tourism. Everything went fine until my carry-on bag passed through the X-ray machine.

A security screener opened my bag and removed the knives. Although he spoke no English, it was clear they were not allowed on the plane.

But instead of tossing my mementos in the trash, he handed them to me and pointed in the direction I had come, back toward the ticket counter. Interpreting this as a suggestion that I might be able to check the knives through, I returned to the ticket counter.

The ticket agent also spoke no English, but nodded knowingly as I held up the knives. Speaking in Uighur, he pointed to the empty luggage conveyor belt

“Well,” I thought, “he’s trying to tell me that my bag has already gone and there’s nothing he can do.” I thanked him and turned to leave.

But he stopped me with a tap on the shoulder and again pointed to the conveyor belt. This time he made a more sweeping gesture from me to the conveyor belt.

Reluctantly, I stepped into the slot where bags are passed though the counter. No objection from the agent.

I walked over to the conveyor belt. Still no protests.

I climbed on to the carousel. The agent smiled and flipped a switch. The belt lurched forward.

I passed through the slit rubber curtain into a dark, cavernous space. My moving sidewalk looped and rumbled through the bowels of the airport. After a while, a faint light appeared, leading through another slit curtain that spilled into a baggage loading area.

The baggage handlers were not at all surprised to see a knife-wielding American emerge from the conveyor belt. They helped me find my bag and I repacked my knives.

Now the only question was: How do I get back to the terminal? No one spoke English, so there was no point asking for directions. Gestures didn’t do much good either.

Seeing no other way out, I turned around, pushed through the slit curtain, double-timed it back up the belt and burst through the top curtain into the check-in area.

The ticket agent was clearly expecting me, since other bags were stacked on the floor in front of the belt awaiting my return.

I bowed to him in thanks, not only for saving my Uighur knife collection, but also for surviving my behind-the-scenes tour of a Chinese airport.

Ron Robins is a retired attorney.

Laptop with antique appearance

More pics at http://m3.alexweidmann.com/piles/?s=steampunklaptop