 |
 | Home | Contact Us | FAQ | Search & Site Map | Link to Us |
 | Sign In | Join | Other 45 Sites in Network |
Natural Science Forum / Physics / Acoustics / August 2005ultrasonic transducers and music
I've been playing around with ultrasonic transducers. I generated two waves of differing frequencies (ex. 75 kHz and 80 kHz) and multiplied them and I heard the 5 kHz tone in the air, which was great, especially since it was directional. I thought that putting a normal sound, like music for example and multiplying it with a 75 or 80 kHz tone, I could hear the music in the air, but only in the slim, directional beam that the transducer generates. However I encountered a problem. The easiest way to mix the two sounds was in matlab, yet the pc sound card just won't do. I tried an higher end sound card but I got nowhere, because the sampling frequency has to be at least twice the highest frequency, so twice 75 kHz, and that is ridiculous. I thought, maybe I can use a wave generator and generate the tone and somehow multiply the sound with the tone. But how would I do that? Or should it be better to do an amplitude modulation with the 2 sources? Can these signal generators do that, i.e. can they take outside signals and mix them with their own generated ones? I'm open to other suggestions as well Cheers, Paul What is the problem with sampling frequencies over 150kHz? The DVD-Audio standard supports sampling frequencies upto 192kHz and, I presume, a cheap home DVD-Audio player will happily play such a DVD. The 192kHz sampling rate is also supported by current cheap soundcards (look at the Creative site for examples). Yes you can AM or FM analogue signals but it is likely to be a lot easier and cheaper messing about in Matlab and using an appropriate GBP 40 soundcard. > I've been playing around with ultrasonic transducers. I generated two > waves of differing frequencies (ex. 75 kHz and 80 kHz) and multiplied [quoted text clipped - 17 lines] > Can these signal generators do that, i.e. can they take outside > signals and mix them with their own generated ones? Since you multiplied them before, what you heard is the 5kHz emitted by the piezo-transducer. You could have as well put those 5kHz directly. You can not radiate any frequencies below the lower limit of the transducer, but you can just feed some high frequency filtered part of the music and you will hear it. You have a loudspeaker, no need for higher frequencies. What you believe you have done is anyway not possible with your setup, because you need at least 2 transducers. And those you have will probably not even radiate 75kHz. The levels must be quite high, so the air gets non-linear and can thus only produce audible mixing frequencies. To get lower frequencies, a lot of air must be moved. Do not fool yourself again. First check out the physical background, then evaluate the needed components, finally make a prototype, if after the research it will still make sense.  Signatureciao Ban Bordighera, Italy >I've been playing around with ultrasonic transducers. I generated two >waves of differing frequencies (ex. 75 kHz and 80 kHz) and multiplied [quoted text clipped - 8 lines] >However I encountered a problem. The easiest way to mix the two sounds >was in matlab, yet the pc sound card just won't do. I tried an higher You need a D/A and something to drive it like Labview. May even need two cards because the mixing may happen in the circuitry instead of in the ear. greg > In article <1123755584.241923.90220@o13g2000cwo.googlegroups.com>, > ballsjohnson@hotmail.com wrote: [quoted text clipped - 14 lines] > May even need two cards because the mixing may happen in the circuitry > instead of in the ear. You don't need two D/A cards and you don't need two transducers and the so- called "mixing" doesn't take place in the ear. If by mixing you mean the generation of a signal at the difference frequency (80KHz-75KHz), that takes place in the air along the path of wave propagation. It's a well documented phenomenon and there are presently two companies that offer products which use that technology. http://www.holosonics.com/ http://www.atcsd.com > I've been playing around with ultrasonic transducers. snip....snip > I'm open to other suggestions as well > > Cheers, > Paul You should be careful where you point those ultrasonic transducers, or you may well find yourself posting as noballsjohnson@hotmail.com. > I've been playing around with ultrasonic transducers. I generated two > waves of differing frequencies (ex. 75 kHz and 80 kHz) and multiplied [quoted text clipped - 19 lines] > > I'm open to other suggestions as well Paul, here's an option: if you know anything about electronics you could make a pair of oscillators out of a couple of XR2206 waveform generators. Those are easily amplitude modulated and can generate frequencies up to 1 MHz or higher. They are also fairly cheap ICs and require only a few support parts (four resistors, 2 capacitors, and one pot to adjust the frequency). Ron Cheap idea: If you have an old reel to reel tape deck: record at the lowest speed play back at a higher speed. "Ron Hubbard" <notat@hotmail.c> >> I've been playing around with ultrasonic transducers. I generated two >> waves of differing frequencies (ex. 75 kHz and 80 kHz) and multiplied [quoted text clipped - 28 lines] > > Ron I guess I could generate a sinus tone with sampling frequency of 150 kHz, for about 2 seconds, I'll just have to leave the pc on all night to finish. Unoftunately I can't do it in realtime, so I cannot demonstrate it with a cd player, for example. Alas, I'm doing a semester abroad and I don't have access to the lab equipment I used before, I'll just have to wait now. Thanks for the posts. I'm not the biggest electronics buff, so I doubt I'll be building anything. The Ghost, the transducers I use have no proven negative effects on the body. snip...snip > The Ghost, the transducers I use have no proven negative effects on the > body. In light of the simplistic nature of your initial post, I doubt that you are an authority on the effects of high intensity ultrasound on human tissue, and in particular on human brain tissue. A case in point is Ron Hubbard who has been experimenting with high-intensity ultrasound for several years. Before he began his experimentation, he was probably just your average, normal person. However, after experimenting with high- intensity ultrasound over a period of several years, he has turned into a total nut case who now sits around in a bathrobe most of the day watching soaps on TV. When he is is not doing that, he is on his computer posting the various soaps newsgroups, posting to various psychic newsgroups and engaged in bizarre discussions with other nut cases in the (his) Yahoo chat group telepaths_empaths_scanning. While you may not care if your testicles turn into rasins, you should give the matter a second thought if you don't want to turn into a nut case like Ron Hubbard. |
Reply to this Message |
 Sign In
 Join
 My Latest Posts My Monitored Threads My Blog My Photo Gallery My Profile My Homepage Start New Thread Enable EMail Alerts Rate this Thread
|
©2009 Advenet LLC Privacy Policy - Terms of Use
This website includes both content owned or controlled by Advenet as well as content owned or controlled by third parties.