QuestionQUESTION: I am looking to generate an audio wave in this range for varmint control. Some subwoofers can go that low, but they are aimed at audiophiles and expensive - I would like the varmints specifically to not like the tone. I considered attaching a vibrating motor to a sheet of metal. Can you give me any tips on my project? Thank you.
ANSWER: Yes, I have heard of these varmint control theories and often wonder if they really work, having had experiences of my own that tend to make me believe that they are only partially effective. Nonetheless, here are my thoughts.
http://www.amazing1.com/pest_control.htm
The above is expensive, but the idea of a variable pulse is an interesting variation that might make it acoustically more ideal for a given size habitation of the critters.
You are right, purchasing a subwoofer, amplifier and oscillator would be expensive but not nearly so much as in the URL above. For example, there are tube type subwoofers with built in amplifier that could drive down into the hole acoustically very nicely. Bazooka makes them and an oscillator to drive the amp would not be expensive, either. It may not be any more expensive than a motor and making your own diaphragm over the critter's hole in the ground. And, if the metal plate is to produce a low frequency component of the acoustic wave it must be back loaded either with an enclosure or by coupling it to the surface of the opening in the ground.
The Bazooka with built in amplifier would cost around $100 plus or minus.
There are many low cost low frequency generator/oscillator circuits that are found with a few googles.
Here is one that works on ultra high frequencies:
http://www.pestnoproblem.com/product/130-0010
Back to your idea of the motor driving a metal plate: It is a simple idea but you would need a slow speed motor with a square plate on the end of the shaft that would vibrate the metal plate. The metal plate must be anchored at the edges to make it vibrate. I have seen this scheme at work so it is easily done. The problem is this; the low frequency acoustic wave is fluidic in nature and the front wave goes around to the back side and cancels the wave. Therefore, you must have some way of preventing the wave from going around the edges of the plate. Either it must be put in a baffle box or mounted directly over the varmint hole in the ground. Lots of experimentation would be necessary to get the right acoustic results, I think.
Let me know your thoughts and we can discuss another round of ideas.
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QUESTION: You found some interesting items that I would not have encountered. The 120 dB sound gun is outside of anything that I've seen. It looks like fun, but kind of dangerous. I noticed that most of the pest control devices are ultrasound-orientated. I happen to know one particular varmint that responds to the 18-19 Hz range.
I came up with another idea: an 18-19 Hz buzzer. Cheap, reliable, easily found and they can low voltage and low volume. Simple! Maybe. The volume is easily controlled by size and power - up to klaxons, were I so inclined. Doubt the neighbors would appreciate a Klaxon ... though I am thinking that a Klaxon is exactly what a car alarm activates.
WHOO --- eeeee --- WHOOO ---- eeeee
The ultrasonic pest repellers are very likely just fancy buzzers tuned to specific frequencies that cause sympathetic vibration in the bones/teeth/ears/eardrums of some targets. I know that some people (me!) absolutely hate the sound of nails on chalkboards. A buzzer that replicated that specific frequency would be an ideal people repellent for most people (but not all).
I also found this:
http://en.wikipedia.org/wiki/Psychoacoustics
... give mice the heebie-jeebies!
Anyways, that's my thought - using a low voltage 18 or 19 Hz buzzer at a tolerable volume (as it's audible to people, right?). The varmints get mostly chased off, or at least discouraged, or distracted. A simple volume control would allow a controllable repellent radius. A solar panel could be attached for power. No need for batteries, low impact and (probably) effective.
AnswerI agree; a buzzer would be a good, low cost way to try it out. And, yes it is going to be audible to humans because the frequency spectrum of buzzer sounds goes to very high multiples of the fundamental frequency. That is why they are called "buzzer" - sorry for the sick humor.
The question in my mind is whether the fundamental rep rate of the buzzer will produce enough low frequency sound to do the job. You will need a really big solar panel to power a buzzer, by the way - and it won't be cheap.
There are more links on the Internet on this subject that can be easily cataloged and many peoples experience with varmints and animals is only anecdotal. The biology and physiology of animals is not well known in this area and there is a lot of witchcraft floating about. I recently encountered the problem of eliminating cockroaches. They DONOT respond to acoustic energy as near as we can tell......
I think you may end up doing some trial and error experimenting to find a suitable solution. You did not say what the animal was so I can't go much further with ideas. A few years ago when living in NJ we had some pesty field varmints (moles) in our back lawn. They had dug up holes all over the place and were getting brave enough to challenge the children playing in the back yard. The only thing that worked, after much trial and error trying to get them to leave, was to pour broken glass down into their holes. We preferred non-lethal strategies but none of them worked - even the chemicals that are thought to do the job! They want away in a few days; whether on their own or from bleeding to death I do not know. We never found any physical evidence of them afterwards. I judge from your question that you don't want to use any "violence" against the little critters!
Hope it helps; let me know the outcome.
Some further reading if you care to do so:
http://www.freepatentsonline.com/6700486.html
http://www.latimes.com/la-me-lopez16-2005nov16,0,2138120.column
(The buzzer didn't work on the Racoons in this one)
http://forums.gardenweb.com/forums/load/pests/msg010831127138.html
And so on........
