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June 14, 2007

Mosquito destruction via acoustics

The resonant frequency idea is apparently more than half-baked.
At least one company, New Mountain Innovations, claims to be able to destroy mosquito larvae up to a five foot radius by sending audio signals at the resonant frequency of the mosquito larvae air bladder. Go Michael! The story is good - now does it really work?

The concept is simple: Use acoustic energy to kill mosquito larvae before they can become biting adults. All mosquito larvae, regardless of species, have internal air bladders that help them breathe and move up and down in the water where they feed and grow. Send sound waves through the water and those bladders start to vibrate like a tuning fork. Eventually the bladder tissue ruptures, killing the larvae.
There is at least one scientific paper on this giving 1 MHz as the frequency of choice.

I'm still hopeful on getting adult mosquitoes in mid-flight. Suppose you were able to send back ultrasound at the frequency the mosquitoes are flapping their tiny wings. Could you (a) cause them to fall to the ground via destructive interference, or (b) cause their wings to rip off via constructive interference? That would a cool demo. The device would need to listen and then replay using large volume the correct frequency. Of course, since you could hear mosquitoes buzzing, perhaps this may not be such a good idea. The frequency here is 250-1000 Hz. Here's some more serious analysis.

Ultrasonic mosquito repellent - will it work?

I was wondering about this all night after a friend of ours mentioned it. Their grandkids are currently in Central Asia getting eaten alive by these little buggers. The question at hand is whether there is anything that technology can offer besides air conditioning, netting and hazardous chemicals. Enter the ultrasonic mosquito repellant. The original theory goes like this - bats, el mosquito's #1 enemy, emit sonar in the 20-50 kHz range. By mimicing these bats, the mosquitoes should take a hike. But does it work? Cecil Adam's straight dope concluded in 1977 "no" based on EPA testing in Chesapeake Bay. The Federal Trade Commission (FTC) and the Center for Disease Control in 2002 said "no" -- this time to a new set of frequencies set to mimic "male mosquitoes and dragonflies".

...ultrasonic products are not effective at preventing mosquito bites. It advises people to:
  • use insect repellent containing DEET, according to the manufacturer's instructions;
  • wear long-sleeved shirts and long pants;
    spread mosquito netting over infant carriers; and
  • stay indoors at dawn and dusk.

As of 2005, the verdict from the CDC was still a resounding "no" -- ""ultrasonic" devices are NOT effective in preventing mosquito bites."

But it is 2006 now. And these things still sell. Perhaps the theory has changed?

Continue reading "Ultrasonic mosquito repellent - will it work?" »

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