Creating 23KHz Ultrasound: Components and Considerations

[MythUser]

Thanks for reading my post.

I would like to produce 23KHz ultrasound at a presure of 70 to 100 dB.

I am thinking that I will need a device to create the 23KHz signal, an amplifier, and either a transducer or a piezo-buzzer.

I'm looking for a point in the right direction.

Are there any off the shelf components that would make this easy?

What sort of signal would be best for driving the output device? (sine, saw-tooth, square, etc.)

Thanks again.

 

[vk6kro]

23 KHz is just slightly above the audio range of human hearing but very obvious to cats and dogs and bats. Maybe you have a barking dog you want to annoy?

Anyway, you could possibly look at some different sorts of tweeters. The better ones probably go well past 22 KHz. Never tried, but a decent audio amplifier feeding into just a tweeter might produce significant output.

Ideally, you might like to borrow a sound level meter that works up there, too. Very high levels of ultrasonic acoustic waves can cause heating of flesh/bone interfaces. Never tried that either. :)

Just sinewaves from an audio signal generator or function generator would be OK.

 

[MythUser]

23 KHz is just slightly above the audio range of human hearing but very obvious to cats and dogs and bats.

Just so. But I believe that only young humans who have never had an inner ear infection and who live in a pre-industrial society can hear anything over 19KHz.

Maybe you have a barking dog you want to annoy?

I wish to train the dog more so than annoy or harm anyone or anything. I would like to teach the dog that one to three barks in a row are fine but continuous barking is not allowed.

Anyway, you could possibly look at some different sorts of tweeters. The better ones probably go well past 22 KHz. Never tried, but a decent audio amplifier feeding into just a tweeter might produce significant output.

If I knew this project were going to be successful then I would not mind buying another receiver/amp just for the project. I have tweeters that say they produce up to 22KHz now but the amp will only handle 20KHz. I doubt the claims of some of the audio vendors already.

Ideally, you might like to borrow a sound level meter that works up there, too. Very high levels of ultrasonic acoustic waves can cause heating of flesh/bone interfaces. Never tried that either. :)

Just sinewaves from an audio signal generator or function generator would be OK.

Thanks for the safety tip. In plastics manufacturing, ultrasound is oft used to weld parts. In that case, the range is direct contact whereas I will be using this at a range of 25 meters. And they use much higher frequencies. It is true, however, that adding any a acoustic wave, from sub to ultra sonic, to a system will add heat to that system. I will be mindful of this whatever I do.

Thanks for the reply, Vk6kro.

 

[vk6kro]

If I knew this project were going to be successful then I would not mind buying another receiver/amp just for the project. I have tweeters that say they produce up to 22KHz now but the amp will only handle 20KHz. I doubt the claims of some of the audio vendors already.

If your amplifier is rated to 20 KHz that is probably just the 3dB point and you could still get a lot of power out at 23 KHz.

The easy way to find out is to do it with your dog in the room and see when he goes cross-eyed. :-)

Or, you could put an oscilloscope across the tweeter and see what sort of voltage you get. About 11.2 volts peak to peak would be 2 watts for an 8 ohm tweeter, which should be plenty.
Otherwise you could set all the dogs in the neighborhood barking.

 

[berkeman]

I will be mindful of this whatever I do.

I sure hope so. If you are doing this anywhere other humans or animals can be affected, you could be setting yourself up for a lawsuit. 25 meters implies that you will be affecting others...

Have you considered a simple bark collar? They haver settings like you described (couple barks okay, more gives a mild training shock), and would not put you in a position of liability with other people and animals.