# How many hertz can kill a flying house insects

1. Jan 18, 2014

### taregg

How many hertz can kill a flying house insects.......

2. Jan 18, 2014

### davenn

hi taregg

none, with the info you have given so far

what are you trying to do.... circuits ??

cheers
Dave

3. Jan 18, 2014

### taregg

How many (sound wave) hertz can kill a flying house insects.......

4. Jan 18, 2014

### davenn

none straight off

BUT maybe if you could find the resonant frequency of the fly or other insect
then produce a sound wave of that frequency at some unknown power level you may be able
to vibrate the insect and kill it .... maybe

Dave

5. Jan 18, 2014

### Bobbywhy

daven above is exactly correct: focused ultrasound can be used to kill insects. Here is a
Chinese patent that does that. Note the translation from Chinese to English is awkward, but the invention's function becomes clear.

"Ultrasonic generator (1) is provided on the front panel power switch (7), the power indicator (8), the frequency adjustment knob (9), power adjustment knob (10), ultrasonic output socket (11). Use the knob to adjust the frequency difference between the two ultrasonic frequency range suitable for use, according to the size of insects killed by properly adjusting power adjustment knob.
Work ultrasonic generator and ultrasonic generating two different frequencies, the frequency difference of the two desired resonant frequency, then the focused ultrasonic transducer can be electric oscillation generator is converted to mechanical oscillations, which produce ultrasonic waves and ultrasound focusing in a range of two ultrasonic certain angle space propagation in air and encounter, both high-frequency and low-frequency sound effect, between the high frequency sound waves are combined, the area A in Figure 2 , low-frequency sound is the difference between the frequency, i.e. the area B in Figure 2, high-frequency sound waves attenuate rapidly in air, when the frequency of the low frequency sound wave frequency in accordance with wings pest or respiratory frequency will resonate, thereby destroying vermin Wings of muscle tissue and respiratory system. So as to achieve the purpose of insecticide.

Now, the OP asked for particular frequency. Here the resultant acoustic power field is "swept" through a certain range of frequencies to resonate with various sizes of insects.

Bobbywhy

6. Jan 18, 2014

### SteamKing

Staff Emeritus
If you get a bug zapper, only 60 (electrical) Hz is required to kill a bug. If you try to zap a bug with sound waves, you could wind up zapping yourself.

You could, however, get a copy of that Chinese patent and swat the bug with it. That would probably be more effective.

7. Jan 18, 2014

### Bobbywhy

Ultrasound, even high peak power pulses, is quite safe for human beings, including the unborn ones.

The OP was not asking about electrical bug zappers that use electricity to kill insects.

Simple physics only explains why, when an insect's body is excited by acoustic frequencies near their body's resonance, they begin to resonate. If the applied pressure waves add in phase, then the insect literarily explodes. No claim about the efficiency or effectiveness of this method was made.

8. Jan 18, 2014

### ChrisVer

I don't believe that resonance can be of any help... Probably because the target is not made by a certain clean material... Finding the resonance frequency would be like trying to find the one which could break a glass- practically very difficult.

9. Jan 18, 2014

### SteamKing

Staff Emeritus
I make my recommendations based on practical observations: you see more electrical bug zappers for sale than acoustical ones. I thought the OP was trying to rid himself of an infestation, but I could be wrong. He might be a nascent mad scientist.

Yes, I know that ultrasound is not harmful to humans, but these are sound waves transmitted by conduction into the body through a transducer. For a practical ultrasonic bug zapper to work, you wouldn't want the user chasing bugs around so he could put a transducer on them, therefore the sound energy must be radiated into a room. It's not clear that radiated sound energy powerful enough to zap a bug won't zap a human or a critical part of a human, like an ear, or objects in the room.

10. Jan 18, 2014

### AlephZero

11. Jan 19, 2014

### Bobbywhy

These passages from the above paper indicate no risk from exposure to airborne ultrasonic frequencies to humans whatsoever:

"For ultrasonic components above 20 kHz, the limits were set to avoid hearing damage in the
audible (lower) frequencies. One-third-octave band levels of 105-115 dB were observed to
produce no temporary hearing loss, and were therefore judged non-hazardous in respect of
permanent hearing damage."

"Since the introduction of these recommended limits, there have been no reports showing
systematic hearing loss trends associated with occupational exposure to very high frequency
noise. Review of the scant literature shows few workers represented, and none with more than
about five years daily contact with potentially harmful noise."

http://www.hse.gov.uk/research/crr_pdf/2001/crr01343.pdf

I may, however, have read over the paper too fast, and may have missed some point which negates the above.

12. Jan 19, 2014

### Bobbywhy

taregg: Flying insects can be killed if they are irradiated by powerful ultrasound. The frequency necessary depends on the physical characteristics of the insect. The idea is to cause the insect's abdomen, for instance, to vibrate so strongly that it explodes, killing the insect. One way of doing this would be to generate an acoustic field that sweeps across a range of frequencies, from say, 40 kHz to 200 kHz, just as the above patent does. When the applied acoustic pressure waves resonate with the insect's body those bodily structures vibrate themselves into destruction. An analogous example is the breaking of a thin glass with a high frequency tone.

None of this theory means that an acoustic insect killer would be effective, or useful, or practical.

13. Jan 19, 2014

### Staff: Mentor

It takes one Hertz to kill a fly. Depending on where you live you may have problems finding a Hertz, as there are only about 2500 Hertzes in US. Probably many more in Germany.

14. Jan 19, 2014

### Lok

An impossible task that is. Although there is a small chance of a "kill" frequency (or multiple combined frequencies) to exist it will only be valid for one exact fly, as small anatomical differences will require a totally different frequency.
As stated by ChrisVer a fly is not a clean material so a sound wave will bounce and be absorbed by any tissue with a different speed of sound, thereby easily reducing the chance of resonance. Like "resonating" a box filled with sand.

15. Jan 19, 2014

### Bobbywhy

You seem to have missed the "sweeping of frequencies" technique. This method insures that the insect will be insonified by the correct resonant frequency, at least momentarily.

16. Jan 19, 2014

### Lok

Yet what do we do if the resonant sound has more than one frequency to it.

17. Jan 19, 2014

### AlephZero

You seem to be contradicting yourself. The quote says there are no harmful effects below the recommended limits. That is not remotely the same as no risk from exposure to airborne ultrasonic frequencies to humans whatsoever.

The paper does conclude that given the relatively small number of people involved with industrial uses of ultrasound (about 0.01% of the UK population), the case for trying to define and set mandatory health and safety limits is not clear cut, compared with a strategy like regular monitoring of the workforce.

It seems rather obvious to me that since the human ear contains mechanical resonant systems of the same dimensions as a typical insect, anything that affects one of those systems enough to permanently stop it from functioning is likely to have some effect on the other system.

18. Jan 19, 2014

### A.T.

Maybe you can control insects with ultrasound.