High pitch sound generator

I have my doubts about how effective it would be. But if you want to do some experiments before you commit to buying any parts, you are welcome to download my DaqGen freeware sound card signal generator. You can see what works and what doesn't, both with respect to frequency and speakers. Note that most sound cards don't go above 20 kHz, even though DaqGen will cheerfully generate higher frequencies internally... you just won't get them out of most cards.

One difficulty might be knowing how well your chosen speaker is working at these frequencies. Might need a young child that still has that part of their hearing range to tell you what is happening.

Best regards,

Bob Masta dqatechATdaqartaDOTcom D A Q A R T A Data AcQuisition And Real-Time Analysis

Home of DaqGen, the FREEWARE signal generator

======================================= Obviously you need a high frequrncy transducer (tweeter!). Get one of those Motrola peizo tweeters at radio shack or the local music store. And a regular old signal generator, maybe one with a burst mode or sweep mode...

"sbl" schrieb im Newsbeitrag news: snipped-for-privacy@h48g2000cwc.googlegroups.com...

I once bought and built an insect repellent kit based on an astable multivibrator. It used an earplug as a loudspeaker. The circuit is very simple and easy to build. And there are plenty of resources available on the net for astable multivibrators. Might be worth checking out. Probably you will need more power and a proper loudspeaker, but I think adding an extra transistor wouldn't be that hard.

Leo

How about a 120 db speaker?

--

50% of all statistics are wrong. The rest don\'t matter.


Clyde Crashcup

BobG wrote: > > On 4 Oct 2006 04:29:32 -0700, "sbl" wrote: > > >I would like to build a home-made cat repeller, based on high pitch > > >sound (18-19KHz and up) > > >What's the simplest way to build such a sound generator? > ======================================= > Obviously you need a high frequrncy transducer (tweeter!). Get one of > those Motrola peizo tweeters at radio shack or the local music store. > And a regular old signal generator, maybe one with a burst mode or > sweep mode...

I tried those tweeters years ago for the neighbors dog. Heathkit audio generator, Sansui amp. Didn't do squat but it was fun fiddling around with it.

GG

Probably the simplest would be a '555 timer with a driver transistor or half-bridge into a piezo tweeter

... Johnny

My experience with dogs is that they do not respond to any sort of sound by itself as a repellent or deterrent to undersirable behavior. My bet is that cats would be the same way.

The sound has to be strongly associated with some sort of punishment, i.e, the sound should probably immediately preceed the punishment or occur concurrently.

Just as an example, and not necessarily a recommendation, you could for instance rig up a cat trap and have the sound start when the trap closes. If cats are like dogs, you would only need to do this once to permanently "train" any individual cat.

Can you explain the half-bridge please.

R

Hello Roger, a simple bi-polar half-bridge would look something like this:-

(View in 'Courier' or 'FixedSys'):-

+Vcc +Vcc o o | | |/ | +---| NPN +---+---+ | |> /| | | | | C +-+ | | '555 +----[R]---+ +---||---| | |SPKR (Piezo-Tweeter) | | | | +++ | +---+---+ | |< | \\| | +---| PNP | | |\\ === === | GND GND === GND

... Johnny

or

Thanks. I see.

Roger

What's the effective range of such a speaker? Do you have any prefered tweeter model?

Thanks,

You might check

for tweeters. They have a big selection and good prices. The problem with most tweeters is gettting frequency response information. Speaker manufacturers don't seem to use the normal -3 dB points to define the frequency range. I'm not sure what criteria they use, but I suspect that it includes a lot of hype. So, don't believe specs like "2000 to 25000 Hz" unless they specify "-3 dB", which they rarely do. Look for an actual curve.

Having said all that, piezo tweeters are probably your best bet if you can't get better info. They tend to have extended high ends, though don't expect them to be flat. (Nothing is very flat at these high frequencies, except maybe electrostatics, and they have other issues.) Piezo tweeters are capacitive loads, with typically pretty high impedance. The efficiency numbers never look too good (typically low 90s for dB SPL at 1 watt and 1 meter) compared to dynamic drivers, but I think that may be because they are not measuring actual power input to the drive, but using an equivalent 8 ohm calculation with the drive voltage. However, if the actual (high) impedance is considered they would be much more efficient. (By the same token, the maximum "power" handling in the specs is also based upon the same fiction, so you aren't going to actually stuff 50 watts or whatever into any piezo tweeter... they just mean that it's appropriate to use as the tweeter with a 50 watt amp driving the overall speaker system with normal program material.)

On the PartsExpress website, look under individual tweeters for specs. I don't recall if there are any response curves for piezos, but under one of them there is a PDF from CTS explaining all the fundamentals and how to calculate the crossover cap, how to use them in series and parallel, etc.

If the underlying concept has any merit, then for good dispersion you might want to go with an array of piezos angled in different directions. You might want to buy an assortment of cheapo models to test, then when you find one you like buy a whole mess of them. They have models priced from under a dollar, in bulk.

Best regards,

Bob Masta dqatechATdaqartaDOTcom D A Q A R T A Data AcQuisition And Real-Time Analysis

Home of DaqGen, the FREEWARE signal generator

Good answer Bob, especially if his question was about 'frequency range', but for some reason, I though he might be asking about 'distance' range, like, from how far away will it annoy the cats? The answer to this depends on how good the cats hear, and how loud the noise is. I think you can put a 25V square wave into those motorola piezos, and at a human audible frequency like 4khz, they are too darn loud to listen to for more than a few seconds at arms length. Assuming they are still that loud at 20khz, I guess we assume they get about 6db quieter every time you double the distance. But to test it, you need to blare it into a cat about 3 feet away and see if he runs away. Then you need to repeat, doubling the distance each time until it becomes ineffective, or until you become shredded from claws.

Range is something you'll need to determine by testing. The simple circuit that I drew would not produce much power, so the range would not be great. A bit of trial and error would be needed to find the right frequency, too. Regarding tweeter models, I vaguely remember that a Motorola tweeter was recommended once for this type of application, but I can't remember what model. I should point out that I personally don't think that these things are very effective. From what I've heard, some people claim that they work and others say they don't. I've seen similar devices marketed either as electronic dog whistles or as 'bark stoppers'. ... Johnny