No, I'm not saying you're like him. I said you reminded me of him. That was when I came to the apparently erroneous conclusion that you were still pursuing wideband modulation of an ultrasonic transducer. I apologize. You are certainly not irritating like he was.
No apologize please,
I am proud becuase I am using your valuable info here, thanks for that.
I am sure those info would help me so much at university (related lessons arrive soon).
We've been telling him this for most of last year Ron, he just doesn't listen!, also the bandwidth of the ultrasonic transducers is far too narrow for sending wideband audio.
Actually, just because you have not heard of one does not mean it does not exist.
They are coming out with ultrasonic directional speakers. Two ultrasonic sources in the same transducer. One is a steady carrier frequency and the other is FM modulated with the audio. The result is that you can have a central audio source sending different audio to different locations without interfering with each other.
Currently some guided tours are doing this with voice grade audio.
Doctors offices use it in the waiting room for TV audio so it does not disturb the receptionists. That was weird, being able to hear the TV walking through the waiting room and not once I got to the desk!
Actually, just because you have not heard of one does not mean it does not exist.
They are coming out with ultrasonic directional speakers. Two ultrasonic sources in the same transducer. One is a steady carrier frequency and the other is FM modulated with the audio. The result is that you can have a central audio source sending different audio to different locations without interfering with each other.
Currently some guided tours are doing this with voice grade audio.
Doctors offices use it in the waiting room for TV audio so it does not disturb the receptionists. That was weird, being able to hear the TV walking through the waiting room and not once I got to the desk!
No, Nigel is talking about conventional ultrasonic transducers, those transducers have 2 or 3KHz of bandwidth.
What you are referring to uses SPECIAl transducers to send 2 ultrasonic waves in the air (200000Hz and 201000Hz for instance), these waves become audible directly in the air due to nonlinear property of the air molecules, this property cause those primary waves to genarate the difference freq (201000-200000=1KHz) which is an audible sound.
No, Nigel is talking about conventional ultrasonic transducers, those transducers have 2 or 3KHz of bandwidth.
What you are referring to uses SPECIAl transducers to send 2 ultrasonic waves in the air (200000Hz and 201000Hz for instance), these waves become audible directly in the air due to nonlinear property of the air molecules, this property cause those primary waves to genarate the difference freq (201000-200000=1KHz) which is an audible sound.
As far as I know AM is used for that task. they don't use 2 sources really,
only one source (or an array of parallel sources) that are fed by AM.
I can remember that I saw a paper about that Technic in the net one day.
hope my brain serves me correctly, they were used AM because the carrier and one (or perhaps 2) sideband can be sent to the air and then the nonliner air demodulates the waves, the result is:
carrierF - one sideband = audio.
That is interesting, is not?
No, Nigel is talking about conventional ultrasonic transducers, those transducers have 2 or 3KHz of bandwidth.
What you are referring to uses SPECIAl transducers to send 2 ultrasonic waves in the air (200000Hz and 201000Hz for instance), these waves become audible directly in the air due to nonlinear property of the air molecules, this property cause those primary waves to genarate the difference freq (201000-200000=1KHz) which is an audible sound.
I know, I was just bringing something to light. Nigel has a tendency to think that because he has not personally heard of something, it does not exist.
Actually it is a form of FM. The difference in the frequencies causes audio when they mix. It disagree, however on the nonlinearity in the air as the audio is not generated until they strike a surface. That surface the becomes then perceived emitter.
I know, I was just bringing something to light. Nigel has a tendency to think that because he has not personally heard of something, it does not exist.
It has no relevence to this thread though, and if you care to search the forums it's been discussed before - with links to sites about it. So kindly keep your ill informed personal comments to your self!.
I know, I was just bringing something to light. Nigel has a tendency to think that because he has not personally heard of something, it does not exist.
Actually it is a form of FM. The difference in the frequencies causes audio when they mix. It disagree, however on the nonlinearity in the air as the audio is not generated until they strike a surface. That surface the becomes then perceived emitter.
Actually, the demodulted audio would be louder as the distance increases.
Hero, you can try it if you have 2 generators and 2 ultrasonic sensors(those how are used in range finding). tune one generator on 40KHz and the other on 41 or 42KHz while the transducers are connected to either generator, now try to hear the whistel while the transducers are side by side near your ear.
Actually, the demodulted audio would be louder as the distance increases.
Hero, you can try it if you have 2 generators and 2 ultrasonic sensors(those how are used in range finding). tune one generator on 40KHz and the other on 41 or 42KHz while the transducers are connected to either generator, now try to hear the whistel while the transducers are side by side near your ear.
42KHz would not have the same effect since the higher the less the beam spread and the louder it remains at distance. I have heard of it being used aat large open air historical sites without volume problems.