Need advice

[Roff]

You mean the strange thing with the 4066?, it's hardly a 'circuit', perhaps a small part of one, that isn't anything like an AM modulator.

But it does put out AM, with the modulating signal added, as I showed in a previous post.

 

[epilot]

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).

 

[epilot]

But it does put out AM, with the modulating signal added, as I showed in a previous post.

Yes Nigel, that is called a 'switching modulator' and works if the bandpass filter be chossen correctly.

 

[cadstarsucks]

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!

D.

 

[epilot]

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!

D.

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.

by the way FM is not used for that arrangement

 

[Roff]

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.

by the way FM is not used for that arrangement

Think about that. If you want to send a frequency other than 1kHz (i.e., audio), you must FM one of the sources. Or is there another way?

 

[epilot]

Think about that. If you want to send a frequency other than 1kHz (i.e., audio), you must FM one of the sources. Or is there another way?

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?

 

[Nigel Goodwin]

Yes Nigel, that is called a 'switching modulator' and works if the bandpass filter be chossen correctly.

But it's not an AM modulator, hence the strange output.

 

[cadstarsucks]

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.

by the way FM is not used for that arrangement

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.

D.

 

[Nigel Goodwin]

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!.

 

[Hero999]

I didn't think that was possible, mixing 201kHz with 200kHz gives a beat frequency of 1kHz but it certainly doesn't give an audiable 1kHz tone.

 

[Roff]

I didn't think that was possible, mixing 201kHz with 200kHz gives a beat frequency of 1kHz but it certainly doesn't give an audiable 1kHz tone.

Hero, Google "holosonics". Pretty amazing stuff.

 

[Roff]

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.

D.

According to Holosonics Research Labs, air nonlinearity is responsible for demodulation.

 

[cadstarsucks]

According to Holosonics Research Labs, air nonlinearity is responsible for demodulation.

OK...I just knew it did not happen until they hit something and was thinking that if it was the "air" that it would happen immediately.

D.

 

[Roff]

OK...I just knew it did not happen until they hit something and was thinking that if it was the "air" that it would happen immediately.

D.

Yeah, it seems like the demodulation would change with distance if it were due to the nonlinearity of air.

 

[epilot]

Yeah, it seems like the demodulation would change with distance if it were due to the nonlinearity of air.

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.

Good luck

 

[cadstarsucks]

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.

Good luck

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.

D.