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Natural Science Forum / Physics / Acoustics / April 2005Making It Loud?
Hi, All; I want to do some experiments with magnetostrictive transducers, particularly rings. I have the idea to fire a jolt of high voltage from an electronic flash unit into a ring of Terfenol- D whose resonant frequency will be about 15 kHz. Does anyone know if some sort of diaphragm is needed to make the sound pulse audible? And if so, what would probably be the best way to go about that? Any help in this would be deeply appreciated. Thanks. Ron -- "You see me now a veteran, of a thousand psychic wars. I've been living on the edge so long where the winds of limbo roar." Singers use a microphone filter called a b filter which can be obtained at music stores. I coat hanger with a womans panty hose stretched over it is what a woman singer I know uses in recording ( much cheaper!). > Hi, All; > [quoted text clipped - 13 lines] > "You see me now a veteran, of a thousand psychic wars. > I've been living on the edge so long where the winds of limbo roar."  SignatureRoger L. Bagula email: rlbagula@sbcglobal.net or rlbagulatftn@yahoo.com 11759 Waterhill Road, Lakeside, Ca. 92040 telephone: 619-561-0814} > Singers use a microphone filter called a b filter which can be obtained > at music stores. I coat hanger with a womans panty hose stretched over > it is what a woman singer > I know uses in recording ( much cheaper!). Hmm... I'm trying to make a sonar-like ultrasonic pulser, only one designed to work in air rather than a medium like water. Once I send a high voltage pulse through a coil wrapped around a ring of some material like nickel, cobalt, Terfenol-D, the ring will oscillate, briefly, at it's resonant frequency converting electricity into sound. But then the problem becomes how to couple that sound source to the air for maximum sound transmission. Ron Use a drum : make the sound hit a drum diaphragm. ( drum diaphragms are nice because you can put particles on them and detect the harmonic shape of the sound.) Another alternative is to make it resonant an organ pipe. It depends on what kind of harmonics you want to set, doesn't it? The b filter takes out vortices as I understand it that are set by "b"'s and "p"'s that mess up microphones by giving popping noises. I thought you were having troubles getting your sounds recorded due to turbulance produced by your method. >>Singers use a microphone filter called a b filter which can be > [quoted text clipped - 13 lines] > > Ron SignatureRoger L. Bagula email: rlbagula@sbcglobal.net or rlbagulatftn@yahoo.com 11759 Waterhill Road, Lakeside, Ca. 92040 telephone: 619-561-0814} > Use a drum : > make the sound hit a drum diaphragm. [quoted text clipped - 7 lines] > I thought you were having troubles getting your sounds recorded > due to turbulance produced by your method. Hi, Roger; I think you kinda have the wrong idea. I"m not trying to record anything; I just want to create a high intensity pulse of 15 kHz sound. Technically, that's ultrasound. but why quibble. But by itself, a magnetostrictive rod or ring-- no matter how hard driven-- won't produce much audible sound all by itself anymore than a bare piezoceramic element; there needs to be a way to couple the magnetostrictive element to the air. It's possible (I guess...) to solder or braze a magnetostrictive rod to a thin steel diaphragm, but how do you do that to a *ring* of nickel, monel, or whatever magnetostrictive metal I choose? I had once built a "sonic screwdriver" that was a masterpiece of electronics and sonic engineering, that could turn screws just by using sound waves alone. The problem was that it took about 143 dB of sound to for it to work, so it was a bit annoying to use.<g> Moving the frequency up to the near ultrasonic range cuts down that problem but now I need to design a better transducer. Magnetostrictive materials have several advantages over piezo elements, but there are a few design problems that are unique to using such elements Ron > I think you kinda have the wrong idea. I"m not trying to record > anything; I just want to create a high intensity pulse of 15 kHz sound. > Technically, that's ultrasound. but why quibble. I built a St Claire type vibrator (15 kHz, 160 dB SPL) for my MS thesis (JASA Jan 1980) ages ago. St. Claire wrote an article about that 'vibrator' in the Review of Scientific Instruments around 1942 or so. > But by itself, a magnetostrictive rod or ring-- no matter how hard > driven-- won't produce much audible sound all by itself anymore than a [quoted text clipped - 3 lines] > thin steel diaphragm, but how do you do that to a *ring* of > nickel, monel, or whatever magnetostrictive metal I choose? Attach a large face on either (or both) end(s) of a rod. > I had once built a "sonic screwdriver" that was a masterpiece of > electronics and sonic engineering, that could turn screws just by using [quoted text clipped - 4 lines] > several advantages over piezo elements, but there are a few > design problems that are unique to using such elements The St Claire had a 4" or 5" diameter face. It was an aluminum bar about 8" long of 6061 Al alloy. Ang. C. > > I think you kinda have the wrong idea. I"m not trying to record > > anything; I just want to create a high intensity pulse of 15 kHz sound. [quoted text clipped - 25 lines] > The St Claire had a 4" or 5" diameter face. It was an aluminum bar about > 8" long of 6061 Al alloy. My screwdriver worked pretty well using a standard Radio Shack piezo "buzzer." Despite what people may say, it is possible to get 143 dB using a piezo transducer-- if it's driven at 200 or 300 volts. I was looking over a PDF file I came across on magnetostrictive materials, and in particular, Terfenol, too get as much as 200 dB of sound using a rod of Terfenol in a Tonpilz design. But my problem is that I am space-limited and can't use a rod more than an inch or an inch and a half long, which would have a much higher than 15 kHz resonant frequency. So I'd like to use a ring, which is much more compact. But how do you attach a diaphragm onto a ring to couple the ring to the air? There, lies my dilemma. Ron > I was looking over a PDF file I came across on magnetostrictive > materials, and in particular, Terfenol, too > get as much as 200 dB of sound using a rod of Terfenol in a Tonpilz > design. That's probably in water. There are many differences between 200 dB in water and 200 dB in air. The first is that the reference pressure is probably different by a factor of 20 (26 dB). The second is the medium is much higher impedance, so equivalent pressure in water equates to much lower sound power. And so on.... > So I'd like to use a ring, which is much more compact. But how do you > attach a diaphragm onto a ring to couple the > ring to the air? There, lies my dilemma. Glue it on with adhesive? I don't se the dilemma. SignatureDave > > I was looking over a PDF file I came across on magnetostrictive > > materials, and in particular, Terfenol, too [quoted text clipped - 12 lines] > > Glue it on with adhesive? I don't se the dilemma. Offhand, if there's something you don't see being done by anybody, there's inevitably a reason why it doesn't work. I don't know the exact physics behind the behavior of magnetostrictive rings, but I do know m.s. rings are very different from piezo-ceramic disks where you can glue a diaphragm directly to the face of a piezo disk. M.s. transducers aren't anything new; they've been around for well over fifty or sixty years now and there hasn't been any radical changes in transducer design in all that period of time; just variations on a theme. And that theme is usually a rod with a diaphragm on at least one face. But ... I suppose I could make an aluminum diaphragm and bolt it onto a ring in some way. Now there's a thought. Ron > But ... I suppose I could make an aluminum diaphragm and bolt it onto a > ring in some way. Now there's a thought. Make its od slightly larger than the id of the ring, press a slight curvature into it and then press that into the ring. Easier said than done, I'm sure, and getting the od right could be tricky but the result should transform the restriction of the ring into axial motion of the diaphragm maximized at its center. Bob Signature"Things should be described as simply as possible, but no simpler." A. Einstein >> But ... I suppose I could make an aluminum diaphragm and bolt it onto a >> ring in some way. Now there's a thought. > > Make its od slightly larger than the id of the ring, press a slight > curvature into it and then press that into the ring. It might be easier to freeze the diaphragm to shrink it, then put it in place and let it expand. Careful lest ye crack the driver (piezo or magnetostrictive). SignatureDave >> But ... I suppose I could make an aluminum diaphragm and bolt it onto a >> ring in some way. Now there's a thought. [quoted text clipped - 8 lines] > > Bob Bob Cain, the self-proclaimed scientist, who recently denied the existence of Doppler distortion and who was incapable of solving a simple partial differential equation for one-dimensional sound propagation in a tube, is now giving advice on the design of resonant ultrasionic transducers. Now that's what I call a real joke. > >> But ... I suppose I could make an aluminum diaphragm and bolt it onto a > >> ring in some way. Now there's a thought. [quoted text clipped - 14 lines] > now giving advice on the design of resonant ultrasionic transducers. Now > that's what I call a real joke. "Ultrasionic transducers"? The only references I found on Google for "ultrasionic transducers" had to do with vaginas and wood. Now that's what I call a joke! > "Ultrasionic transducers"? The only references I found on Google for > "ultrasionic transducers" had to do with vaginas and wood. Now that's > what I call a joke! It's "ultrasonic" you moronic swine. > > "Ultrasionic transducers"? The only references I found on Google for > > "ultrasionic transducers" had to do with vaginas and wood. Now that's > > what I call a joke! > > It's "ultrasonic" you moronic swine. Look at what you wrote in your post. That's why I put "Ultrasionic transducers" in quotation marks, I was quoting you, you senile old fool! BTW, I mean that in the nicest way. :-) >> > "Ultrasionic transducers"? The only references I found on Google for >> > "ultrasionic transducers" had to do with vaginas and wood. Now that's [quoted text clipped - 5 lines] > transducers" in quotation marks, I was quoting you, you senile old fool! > BTW, I mean that in the nicest way. :-) Pigs were never known for their intelligence, and you are certainly no exception. Only a mindless swine such as yourself would take an obvious typo literally and, worse yet, make a childish and pathetic attempt at portraying it otherwise. The truth of the matter is that the only one who is old, senile and a fool is you. By the way, what ever happened to the numerous times that you asserted that you were placing me in your (permanent) kill file. Perhaps you should check your (permanent) killfile because it is obviously not working. . > >> > "Ultrasionic transducers"? The only references I found on Google for > >> > "ultrasionic transducers" had to do with vaginas and wood. Now that's [quoted text clipped - 15 lines] > you were placing me in your (permanent) kill file. Perhaps you should > check your (permanent) killfile because it is obviously not working. Typo's are mechanical errors caused by the fingers, your consistant spelling and grammatical errors would seem to indicate mental deficiency. As for the killfile, I just did a re-install of XP on my computer, and when I re-subscribed to this group, the killfile was erased, so I'll have to fix that. BTW, I have to apologize for the "senile old fool" phrase, obviously I meant, "doddering, senile old fool" Have a nice day PLONK! (no typo) SignatureRoger W. Norman SirMusic Studio http://blogs.salon.com/0004478/ > >> > "Ultrasionic transducers"? The only references I found on Google for > >> > "ultrasionic transducers" had to do with vaginas and wood. Now that's [quoted text clipped - 17 lines] > > . > PLONK! (no typo) Agreed. Listen up. By now, we all know how to make filters that work. Go to it. Angelo Campanella > > PLONK! (no typo) > [quoted text clipped - 5 lines] > > Go to it. Where did that filter idea come from? I was asking about a magnetostrictive acoustical transducer-- a way to produce a lot of sonic energy in and through air. The very last thing that I needed was a filter. Ron > Where did that filter idea come from? I was asking about a > magnetostrictive acoustical transducer-- a way to produce a > lot of sonic energy in and through air. The very last thing that I > needed was a filter. Ron, we are talking about a Ghost filter. It's of the notch type. Most news readers will allow you to filter out postings based on the sender so that you don't have to see what they post. Bob Signature"Things should be described as simply as possible, but no simpler." A. Einstein In sci.physics, Bob Cain <arcane@arcanemethods.com> wrote on Sat, 26 Mar 2005 01:40:58 -0800 <d23anb0vss@enews3.newsguy.com>: >> Where did that filter idea come from? I was asking about a >> magnetostrictive acoustical transducer-- a way to produce a [quoted text clipped - 5 lines] > postings based on the sender so that you don't have to see > what they post. Just be careful; there are two Ghosts about. :-) Hopefully I'm the more intelligent one. (I'm also the Earthlink one, as you can probably see in my Path: header.) As for filters -- they come in various forms; the usual terms I've heard are "killfile", "scorefile", or "krillfile". The exact terminology probably depends on the newsreader. As for magnetostrictive acoustical transducers -- an interesting notion. One might be able to excite the water (since water has an electrical dipole moment, it's about the only candidate I can think of in the atmosphere that might even respond to a magnetic field, though were one talking about gaseous iron one might get into interesting -- but extremely hot -- territory). Oxygen also is paramagnetic in its liquid form, which means it might respond to the hypothetical transducer. I can't say I've heard of any research in that area -- but then, I'm not in that area; my field involves computer software development. :-) http://www.webelements.com/webelements/elements/text/O/key.html Unfortunately, nitrogen does not have a similar comment, so I don't know how it will respond to a magnetic field. http://www.webelements.com/webelements/elements/text/N/key.html (How does one sniff a liquid that will freeze one's nose off? :-) ) I'm somewhat curious as to the construction of the OP's magnetorestrictive transducer coil. As one well knows, transformers tend to hum (in older model TV sets, they in fact scream, but that's because they operate at 15,750 Hz as opposed to power transformers' 60). It's not clear to me whether this hum will interfere with the OP's objective or not; if one is constructing a high-quality loudspeaker it might, but if one is constructing a weapon, it might not matter too much unless the enemy hears the weapon prior to the firing thereof... :-) > Bob Signature#191, ewill3@earthlink.net It's still legal to go .sigless. > Just be careful; there are two Ghosts about. :-) Hopefully > I'm the more intelligent one. Intelligence isn't established by hope. Furthermore, if you are of such superior intelligence, as you hope, why in God's name would you even want to involve yorself this feud? In sci.physics, The Ghost <theghost@sbcglobal.net> wrote on Sun, 27 Mar 2005 03:24:48 GMT <Xns9625C5916CBA8theghosthotmailcom@140.99.99.130>: > >> Just be careful; there are two Ghosts about. :-) Hopefully [quoted text clipped - 4 lines] > to involve yorself this feud? > Oh well, in that case then I must concede, you're the more intelligent one here, obviously. Followups. Signature#191, ewill3@earthlink.net It's still legal to go .sigless. > Ron, we are talking about a Ghost filter. It's of the notch > type. Most news readers will allow you to filter out > postings based on the sender so that you don't have to see > what they post. > Bob The Ghost has yet to be shown to be wrong on any technical issue. Unfortuantely the same can not be said for Bob Cain. Do a Google Search on Bob Cain and Doppler distortion and, in particular, "Bob Cain goes down and out in defeat." > Ron, we are talking about a Ghost filter. It's of the notch > type. Most news readers will allow you to filter out > postings based on the sender so that you don't have to see > what they post. > Bob Alternatively, let me recommend that you utilize a Bob Cain filter. It too is of the notch type, and it will protect you against the detrimental and disasterous consequences of taking seriously anything further that Bob Cain has to say. In this regard, I can't imagine why would you even consider taking seriously anything that Bob Cain has to say. He recently denied the existence of Doppler distortion in loudspeakers which was analyzed and established over thirty years ago. Furthermore, even though he proclaims himself to be a scientist, he was unabale to solve a trivial partial differential equation for one-dimensional wave propagation in a tube. Bob Cain is a technically inpept ignoramus and a fraud and it is time for all of his admirers to stop their denial and get a reality check. >> PLONK! (no typo) > [quoted text clipped - 7 lines] > > Angelo Campanella There is another solution, and I thank you for your support. Mike, I only know when this psychopath has thrown more venom my way when others respond to it. I have him globally kill filed and I would urge you to do the same. Bob Signature"Things should be described as simply as possible, but no simpler." A. Einstein > Mike, I only know when this psychopath has thrown more venom > my way when others respond to it. I have him globally kill > filed and I would urge you to do the same. > > Bob Yeah, I did, but as I explained in my previous reply to the ghost, I did an XP re-install and accidentally erased my killfile when I re-subscribed to the news server. Fortunately that is easily fixed, especially since the ghost was the only person irritating enough to be placed in my killfile. I hope he appreciates that distinction! :-) > Yeah, I did, but as I explained in my previous reply to the ghost, I > did > an XP re-install and accidentally erased my killfile when I > re-subscribed to the news server. Fortunately that is easily fixed, > especially since the ghost was the only person irritating enough to be > placed in my killfile. I hope he appreciates that distinction! :-) Excuses....excuses......but that's pretty much what everyone has come to expect from porky the pig in the swine pen. Hoepfully porky will get his problem fixed asap, so that no one will be subjected to his mindless and nonsensical replies to my posts in the future. BYW, Easter is only a few days away and it's that time of the year when pigs serve there only useful purpose. > > Yeah, I did, but as I explained in my previous reply to the ghost, I > > did [quoted text clipped - 12 lines] > BYW, Easter is only a few days away and it's that time of the year when > pigs serve there only useful purpose. At least pigs have a purpose, ghosts only annoy. >> > Yeah, I did, but as I explained in my previous reply to the ghost, I >> > did [quoted text clipped - 14 lines] >> > At least pigs have a purpose, ghosts only annoy. Ghosts only annoy pigs and jackasses. Speaking of jackasses, Jim Carr is really slipping. I intentionally included the grammatical error (there vs their) solely to get his attention, and I am really disappointed that he missed it. > Mike, I only know when this psychopath has thrown more venom > my way when others respond to it. In addition to being a technically-inpet fraud and liar, Bob Cain is the consummate hypocrite and a contemptable piece of human waste. Anyone who wants to waste their time checking Bob Cain's posting record (Google Groups) will find that he posesses in spades all of the traits that he routinely condemns in others, and that his present post is no exception. > > Mike, I only know when this psychopath has thrown more venom > > my way when others respond to it. [quoted text clipped - 4 lines] > Groups) will find that he posesses in spades all of the traits that he > routinely condemns in others, and that his present post is no exception. That would be inept (not inpet), possesses (not posesses) and contemptible (not contemptable). Really, Ghost, if you're going to insult someone's intelligence, the very least you can do is try not to appear illiterate. >> > Mike, I only know when this psychopath has thrown more venom >> > my way when others respond to it. [quoted text clipped - 10 lines] > insult someone's intelligence, the very least you can do is try not to > appear illiterate. What, if it weren't for my typos, would you mindlessly whine about? > >> > Mike, I only know when this psychopath has thrown more venom > >> > my way when others respond to it. [quoted text clipped - 12 lines] > > What, if it weren't for my typos, would you mindlessly whine about? Your mindless posts, perhaps? Your lack of intelligence is exceeded only by your ineptitude at inventing creative insults. You're no fun at all. Back when I was fueding with Jim, I was forced to acknowledge his mastery of the insult as a high art form. You're just an idiot with a computer, and I doubt even a thousand of you pecking away on your collective keyboards could come up with even one creative insult! > Your mindless posts, perhaps? Your lack of intelligence is exceeded > only > by your ineptitude at inventing creative insults. You're no fun at > all. Thank you for bestowing upon all of the readers of these newsgroups your pig-founded enlightenment. I, for one, was previously unaware that one's intelligence is judged on the basis of their aptitude at inventing creative insults. Unfortunately, when that course on creative insults was offered, I missed it because I had already signed up for courses in linear systems theory and advance engineering math. Perhaps that's why I was correct and you, Bob Cain and Jim Carr were wrong on every aspect of the issue of Doppler Distortion. > Back when I was fueding with Jim, I was forced to acknowledge his > mastery of the insult as a high art form. You're just an idiot with a > computer, and I doubt even a thousand of you pecking away on your > collective keyboards could come up with even one creative insult! Call me whatever you wish, but given that you don't have the professional credentials to back up your insults/assertions, they mean nothing. The fact that you admire Jim Carr for his so-called "mastery of the insult as a high art form" speaks volumes about your mentality and your total lack of character. > > Your mindless posts, perhaps? Your lack of intelligence is exceeded > > only [quoted text clipped - 9 lines] > you, Bob Cain and Jim Carr were wrong on every aspect of the issue of > Doppler Distortion. You didn't prove anything on the issue of Doppler distortion, and in fact, your input wasn't even related to the issue of Doppler distortion in a speaker! We all know you're lying about your "qualifications" because we all know that they don't allow ghosts to attend college. > > Back when I was fueding with Jim, I was forced to acknowledge his > > mastery of the insult as a high art form. You're just an idiot with a [quoted text clipped - 6 lines] > high art form" speaks volumes about your mentality and your total lack of > character. Actually, I do have the professional credentials to back up my insults/assertions, I hold an advanced doctorate in Insultology and a masters in Assertonomy from Vanderbilt University. Strange that a ghost, which represents a total lack of everything, should comment on anyone's character. > You didn't prove anything on the issue of Doppler distortion, and > in fact, your input wasn't even related to the issue of Doppler > distortion in a speaker! The problem was not with the relevance of what I said/did, the problem was and continues to be with your inability to recognize/acknowledge it. > We all know you're lying about your > "qualifications" because we all know that they don't allow ghosts to > attend college. You all know nothing whatsoever about my qualifications. Nonetheless, you are correct that "they" don't allow ghosts to attend college, but I attended college and graduate school before I became a ghost. > Actually, I do have the professional credentials to back up my > insults/assertions, I hold an advanced doctorate in Insultology and a > masters in Assertonomy from Vanderbilt University. Let me also add your doctorate in moronology. > Strange that a ghost, which represents a total lack of everything, > should comment on anyone's character. What is really strange is that a pig would comment on anything. Ghosts have souls...pigs don't. Pigs eat garbage, roll in the mud, grunt, get killed and then eaten. Ghosts live forever. > > You didn't prove anything on the issue of Doppler distortion, and > > in fact, your input wasn't even related to the issue of Doppler > > distortion in a speaker! > > The problem was not with the relevance of what I said/did, the problem was > and continues to be with your inability to recognize/acknowledge it. No, the problem is that you can't see that there is a difference between a speaker cone driven by a single complex source vibrating at multiple frequencies and, and a speaker cone vibrating at one frequency while the speaker is being moved by an entirely different source. > > We all know you're lying about your > > "qualifications" because we all know that they don't allow ghosts to [quoted text clipped - 3 lines] > are correct that "they" don't allow ghosts to attend college, but I > attended college and graduate school before I became a ghost. Yeah, sure. Look, we all know that you employed a ghostwriter for your part of the technical paper cowriten with Jensen. > > Actually, I do have the professional credentials to back up my > > insults/assertions, I hold an advanced doctorate in Insultology and a > > masters in Assertonomy from Vanderbilt University. > > Let me also add your doctorate in moronology. By george, you're right, I did forget that one! "Moronology" would be the study of morons, and I get a refresher course every time I read one of your posts! > > Strange that a ghost, which represents a total lack of everything, > > should comment on anyone's character. > > What is really strange is that a pig would comment on anything. Ghosts > have souls...pigs don't. Pigs eat garbage, roll in the mud, grunt, get > killed and then eaten. Ghosts live forever. Ghosts don't have souls, because ghosts don't exist. Pigs have brains, ghosts don't, because if the ghost doesn't exist neither does its brain.. Pigs may die, but ghosts, being nonexistant, never live at all. At least pigs are good for something. Ghosts are totally useless! > No, the problem is that you can't see that there is a difference between > a speaker cone driven by a single complex source vibrating at multiple > frequencies and, and a speaker cone vibrating at one frequency while the > speaker is being moved by an entirely different source. To continue on an acoustic line ... I have difficulties seing the vital significance of that difference on the sound field created by the loudspeaker. In fact the only difference I see is that there will be a contribution from the frame of the loudspeaker. But that is not likely to affect the modulation of the diaphragm-signal, at least not within the level of details we are discussing here. Would you kindly elaborate on the difference? regards Peter >> No, the problem is that you can't see that there is a difference >> between [quoted text clipped - 16 lines] > regards > Peter Don't hold your breath waiting for any reply from porky the mindless and cowardly pig, let alone an intelligent, sensible and coherent reply. > Don't hold your breath waiting for any reply from porky It seems you are right. I had hoped for a constructive contribution from him. best regards Peter >> Don't hold your breath waiting for any reply from porky > [quoted text clipped - 3 lines] > best regards > Peter The lack of a reply might be because the pig doesn't read alt.sci.physics.acoustics and because you didn't cross-post your question to alt.music.home-studio where he hangs out. He probably won't read this either if his kill file is finally working. > The lack of a reply might be because the pig doesn't read > alt.sci.physics.acoustics and because you didn't cross-post your question > to alt.music.home-studio where he hangs out. He probably won't read this > either if his kill file is finally working. Well, I don't have access to the alt.music.home-studio from my newsserver. Anyhow, if he writes here he ought to read here. best regards Peter > > No, the problem is that you can't see that there is a difference between > > a speaker cone driven by a single complex source vibrating at multiple [quoted text clipped - 11 lines] > > Would you kindly elaborate on the difference? Certainly! The complex waveform driving the speaker cone is a single gestalt, and the cone motion reflects that. Driving a speaker cone with a single frequency while moving the speaker at a different frequency results in two different motions from two different motive sources, an analogy of the whistle on a moving train. The speaker cone driven by a complex waveform would be more analgous to a diaphragm over a hole in a wall between the source and the listener. > Certainly! The complex waveform driving the speaker cone is a single > gestalt, and the cone motion reflects that. Driving a speaker cone with a [quoted text clipped - 3 lines] > would be more analgous to a diaphragm over a hole in a wall between the > source and the listener. Thanks. The explanation doesn't satisfy my engineering mind. Gestalts etc are very vague to me. Can you explain in more details, for a point on the diaphragm, what the difference in movements would be in the two situations? best regards Peter > > Certainly! The complex waveform driving the speaker cone is a single > > gestalt, and the cone motion reflects that. Driving a speaker cone with a [quoted text clipped - 8 lines] > Can you explain in more details, for a point on the diaphragm, what the > difference in movements would be in the two situations? Ah, but that's why I stay in home-studio and don't post here except in answer to the ghost's misguided cross-posts (which won't happen again because I've placed him in my killfile again, hopefully, this time permanently). I don't have the math and physics background to explain it, but it seems obvious to me there is a huge difference between a whistle on a moving train (a speaker cone vibrating at one frequency while the speaker is moved at another) and a diaphragm over a hole in the wall between the sound source and a listener (a speaker being driven by a complex waveform containing multiple frequencies, i.e., music!). If someone with the math and physics background and an objective view (not predisposed to either side of the issue) wants to do the math and prove it one way or the other, that's fine with me, but this is the limit of my input on the subject. The difference seems obvious to me for several reasons, but that doesn't necessarily mean that there really is a difference. Simply put, assuming that the movement of the diaphragm over the hole in the wall is faithful to the sound pressure waves coming through the hole in the wall, I don't see how Doppler distortion could be induced, and a high fidelity speaker reproducing music would certainly be the analog of a hole in the wall, or acoustical "window" to the original live performance. > I don't have the math and physics background to explain it, but it seems > obvious to me there is a huge difference between a whistle on a moving train > (a speaker cone vibrating at one frequency while the speaker is moved at > another) and a diaphragm over a hole in the wall between the sound source > and a listener (a speaker being driven by a complex waveform containing > multiple frequencies, i.e., music!). Well, I better admit that I am pre-disposed. But I wouldn't mind being convinced by good arguments. I do think, however, that your analogies are misleading, in that they don't deal with comparable situations. It is like comparing apples to pears, where we should be comparing different sorts of apples. There is no mystery to complex wave-forms. As the term is used here, it simply related to the juxtaposition of different frequencies. It is important to understand that the diaphragm movements will not contain the two signals "in parallel". There won't be two "independent" movements. In stead, the two frequencies are put on top of each other, and the lower frequency will constantly change the "rest position" of the higher frequency. I also don't like the "diaphragm over the hole" analogy. If you consider a loudspeaker diaphragm, it spends most of its working time outside the hole. Those movements are what creates the sound from the loudspeaker. As I recall the previous discussions, the final disagreement between The Ghost an Bob Cain ended up being a play on words. They agreed that there would be modulations when two tones were presented simultaneously, but disagreed whether these modulations should be called Doppler-effects or not. The actual influence of these modulations on more complex signals than just two-tone signals, may not be alarming. But they certainly do exist. > Simply put, assuming that the movement of the diaphragm over the hole in > the wall is faithful to the sound pressure waves coming through the hole in > the wall, I don't see how Doppler distortion could be induced, and a high > fidelity speaker reproducing music would certainly be the analog of a hole > in the wall, or acoustical "window" to the original live performance. Simply put, the movement of the diaphragm is not a faithful reproduction of the sound pressure in the hole, for the exact reason that the diaphragm spends most of its time outside the hole. Peter > > I don't have the math and physics background to explain it, but it seems > > obvious to me there is a huge difference between a whistle on a moving train [quoted text clipped - 37 lines] > of the sound pressure in the hole, for the exact reason that the > diaphragm spends most of its time outside the hole. Whether the diaphragm stays in the hole or not depends on the thickness of the wall. In a perfect loudspeaker, the cone motion would follow the driving signal exactly, as would a perfect, massless diaphragm over a hole in the wall. I think it would be fairly obvious that in the case of a perfect speaker or a perfect diaphragm, there would be no Doppler Distortion introduced (in fact, no distortion of any kind), since the soundwave produced would be a perfect copy of the original. Other forms of distortion, of course, will appear in the imperfect real world speaker, but Doppler won't be among them. That's my take on it, because due to the nature of Doppler distortion, it would appear even in the "perfect" diaphragm, and assuming that the perfect diaphragm reproduces a perfect copy of the original soundwave, distortion of any type, including Doppler distortion, wouldn't be generated unless it was present in the original wave, and if it were present in the original wave, then it would already be there, and wouldn't be generated by the perfect speaker/diaphragm. The logic may seem circular, but it isn't. Have fun debating it, because that's as far as I'm going with it. :-) > Whether the diaphragm stays in the hole or not depends on the thickness of > the wall. In a perfect loudspeaker, the cone motion would follow the driving [quoted text clipped - 3 lines] > introduced (in fact, no distortion of any kind), since the soundwave > produced would be a perfect copy of the original. You are right in that the cone motion will follow the driving signal exactly. And that is the reason that it doesn't matter if the loudspeaker chassis is fed with the one frequency and the cone with the other, or the cone with the sum of the two signals. But I think you are very unclear about the driving signal and its source. If the massless diaphragm moves in a hole of any thickness, it will not reproduce the sound pressure in a fixed point in the middle of the hole. It will rather reproduce the average movements of the air molecules that transmit the sound pressure wave. I also think you disagree with Bob Cain in your statements above. If I remember it correctly, he admitted to the modulations but disagreed with the term doppler distortion. I don't know your age, but I will presume you remember some of the odd amplifier classes from the late 70'es. One of them consisted of a low voltage class-A amplifier. When large signal amplitudes were required, then a class-B amplifier would modulate the potential of the power supply. So in stead of being fed with (something like) +/-12V it was fed with (something like) a varying +46V/+22V to -22V/-46V. Using this technology, the output signal could reach +/-46V. You can do the same with loudspeakers. If you feed the cone with +/- 2mm of sinusoidal motion (excuse me for my non-scientific trade with units) and the chassis with +/-2 cm of the same sinusoidal motion then it will produce the same loudness as if you had fed the cone with +/- 2.2 cm of motion. And you can likewise cancel the sound from the cone, if you feed the chassis with exactly the same motion in opposite phase. And, if you feed the cone with a 2mm-excursion 300 Hz tone + a 2mm 2500 Hz tone, then it will demontrate exactly the same movements as if you feed the cone with the 2mm-excursion 300 Hz one and the chassis with a 2mm 2500 Hz tone. This is my understanding of things, which you contradict. However, your contradiction is without much substance or argument or example. Taken that there is no substantial contradiction of my understanding, the Ghost's experiment must be valid. The only source of error I see in it, is the contribution from the frame of the loudspeaker, which will tend to increase the low-frequency component in relation to both the high frequency component and the distortion products. best regards Peter > This is my understanding of things, which you contradict. However, > your contradiction is without much substance or argument or example. [quoted text clipped - 3 lines] > will tend to increase the low-frequency component in relation to both > the high frequency component and the distortion products. The radiated low-freqeuncy component was at an extremely low level because of the very small size of the frame (25mm dia) relative to the wavelength of the low-frequency sound (17 meters at 20Hz). For all practical purposes, the only radiated sound that was measurable (above the system noise floor) consisted of the 10KHz carrier that was generated by the 12mm dia piezoelectric bimorph and the FM sidebands that were produced by the low-frequency (20Hz) whole-body motion. > I also think you disagree with Bob Cain in your statements above. If I > remember it correctly, he admitted to the modulations but disagreed with > the term doppler distortion. Yes, in a plane wave there is a non-linear relationship between the motion of the particles about a point, which is what is usually controled with a loudspeaker, and the pressure at that point, which is what a pressure transducer would detect. My analysis showed that the phase relationship between those distortion components and what causes them is not what would be required to call it Doppler distortion as that is usually defined. The distortion maxima occur when the oscilating particles are at the extreme of their LF oscilation with zero LF velocity the minima occur when they are moving at maximum LF velocity through their rest position. What occurs when, OTOH, you put a HF source on a swing going at some LF will look like traditional Doppler distortion. There is a difference in what is measured in that case, where the LF source is decoupled from the receiver, and what happens when the same motion is given a piston in a tube where it remains fully coupled. Bob Signature"Things should be described as simply as possible, but no simpler." A. Einstein > What occurs when, OTOH, you put a HF source on a swing going at some LF > will look like traditional Doppler distortion. There is a difference in > what is measured in that case, where the LF source is decoupled from the > receiver, and what happens when the same motion is given a piston in a > tube where it remains fully coupled. That's interesting, because that is what I don't grasp (meaning I think you are wrong). Can you explain the difference to me, like setting up a motion equation for the HF source diaphragm in the two cases? best regards Peter >> What occurs when, OTOH, you put a HF source on a swing going at some >> LF will look like traditional Doppler distortion. There is a [quoted text clipped - 9 lines] > best regards > Peter Apparently Bob Cain has decided to keep the explanation that you requested a secret. > Yes, in a plane wave there is a non-linear relationship > between the motion of the particles about a point, which is > what is usually controled with a loudspeaker, and the > pressure at that point, which is what a pressure transducer > would detect. That is total nonsensical drivel. At low and moderate sound pressure levels, where air nonlinearity is not a significant factor, pressure and particle velocity in a plane wave are directly proportional. The nonlinear relationship between piston motion and resultant plane-wave pressure is due to the finite excursion of the piston, as Art Ludwig has correctly pointed out. It is for this reason that (Doppler) intermodulation distortion is reduced as piston area is increased and piston displacement is reduced while maintaining the same piston volume velocity. > My analysis showed that the phase > relationship between those distortion components and what > causes them is not what would be required to call it Doppler > distortion as that is usually defined. What analysis? Where has it been presented, and where have you compared the predictions of your analysis with measurements that substantiate its validity and your assertions? > The distortion > maxima occur when the oscilating particles are at the > extreme of their LF oscilation with zero LF velocity the > minima occur when they are moving at maximum LF velocity > through their rest position. What exactly is your definition of the dynamic non-steady-state distortion to which you refer, and what measurements do you have to support your assertion? > What occurs when, OTOH, you put a HF source on a swing going > at some LF will look like traditional Doppler distortion. > There is a difference in what is measured in that case, > where the LF source is decoupled from the receiver, and what > happens when the same motion is given a piston in a tube > where it remains fully coupled. This absurd and nonsensical issue of coupling is nothing more than a figment of your technically-inept imagination. The only difference between the far-field pressure produced by a vibrating piston an infinite wall and the pressue produced by a vibrating piston in an infinite tube is that in the former pressure is proportional to piston acceleration, whereas in the latter, pressure is proportional to piston velocity. In both situations, FM (Doppler) distortion is produced and its magnitude is solely related to pistion excursion. > > Whether the diaphragm stays in the hole or not depends on the thickness of > > the wall. In a perfect loudspeaker, the cone motion would follow the driving [quoted text clipped - 46 lines] > tend to increase the low-frequency component in relation to both the > high frequency component and the distortion products. I agree that here in the real world, distortion of several sorts will arise, both from the driving signal, which is not perfect, and from the speaker, even when driven in its linear range, because of all sorts of things. I just don't think any of these forms of distortion has anything to do with the Doppler effect. I realize that my view may not seem to be particularly scientific, but I've also seen that people bring all sorts of arguments to bear that have absolutely nothing to do with the Doppler effect. I follow the math well enough to see that no one so far has proven that any of the distortion from a speaker has anything to do with the Doppler effect. Also, due to the effects of inertia and other things, it seems obvious to me that driving a speaker cone with one signal while moving the speaker with another is totally different from driving a speaker cone with a single complex signal, and I fail to see how othere don't grasp that. This argument has been going on since at least the early 1950's and some of the best minds in acoustics haven't been able to prove anything either way. I have my views and I understand that others will have other views, so I'll stop here, if for no other reason than I can't provide solid proof of my views, and I'm aware that I may be wrong. :-) > I realize that my view may not seem to be particularly scientific, > but [quoted text clipped - 16 lines] > provide solid proof of my views, and I'm aware that I may be wrong. > :-) You are wrong, and everything that you have said is nonsensical drivel. > Also, due to the effects of inertia and other things, it seems obvious to > me that driving a speaker cone with one signal while moving the speaker with > another is totally different from driving a speaker cone with a single > complex signal, and I fail to see how othere don't grasp that. The funny thing is that if you put up a motion equation for the diaphragm in the two cases, then the results end up being identical. BTW - beware of the obvious! > This argument has been going on since at least the early 1950's and some > of the best minds in acoustics haven't been able to prove anything either > way. I have my views and I understand that others will have other views, so > I'll stop here, if for no other reason than I can't provide solid proof of > my views, and I'm aware that I may be wrong. :-) Keep on reading. Peter >>it seems obvious to me that driving a speaker cone with one signal while moving the >> speaker with another is totally different from driving a speaker cone with a single >> complex signal, and I fail to see how othere don't grasp that. It's 'totally different' only in that moving the speaker vs driving the speaker with a complex signal introduces two different speeds as the low frequency component. It rally adds a third (swing) speed. I think that carrying a boom box on a swing merits the best of our cracker barrel analysis efforts, for those that care to indulge such things! Angelo Campanella >>> it seems obvious to me that driving a speaker cone with one signal >>> while moving the speaker with another is totally different from [quoted text clipped - 4 lines] > speaker with a complex signal introduces two different speeds as the low > frequency component. Is it so, if we make a proper compensation (=amplification) of the larger mass when driving the entire frame? > It rally adds a third (swing) speed. How is that different from driving the cone with the complex? > I think that > carrying a boom box on a swing merits the best of our cracker barrel > analysis efforts, for those that care to indulge such things! Rather carrying a tweeter on a swing. A boom box on the swing sounds like two low frequency components. best regards Peter > Rather carrying a tweeter on a swing. A boom box on the swing sounds > like two low frequency components. The tweeter on a swing is a different situation than a piston in a tube having the same motion in that the LF motion in the first case is _through_ the air and not really coupled to it in an acoustic sense. In the second, both the HF and the LF are equally coupled to the air. Should this not make a difference in the way the two components mix to form intermodulation products? Bob Signature"Things should be described as simply as possible, but no simpler." A. Einstein > The tweeter on a swing is a different situation than a piston in a tube > having the same motion in that the LF motion in the first case is [quoted text clipped - 3 lines] > Should this not make a difference in the way the two components mix to > form intermodulation products? Not really. It's more a difference between spherical an plane sound waves. The high frequencies would be modulated in the same way, even if the low frequency component isn't audible per se. best regards Peter > > Also, due to the effects of inertia and other things, it seems obvious to > > me that driving a speaker cone with one signal while moving the speaker with [quoted text clipped - 5 lines] > > BTW - beware of the obvious! If your equations take into account the inertia of the speaker cone and the fact that it isn't rigidly attached to the speaker frame when you're moving the whole speaker back and forth, you might note that the comparative results won't be identical. Other factors come into play as well. > > This argument has been going on since at least the early 1950's and some > > of the best minds in acoustics haven't been able to prove anything either [quoted text clipped - 3 lines] > > Keep on reading. I will! :-) > If your equations take into account the inertia of the speaker cone and the > fact that it isn't rigidly attached to the speaker frame when you're moving > the whole speaker back and forth, you might note that the comparative > results won't be identical. What kind of influence should it have? In the standard setup, with a relative low-Q unit, a voltage source amplifier, signals above the f0, operation within the linear excursion I don't see what influence you would expect. Acoustically, the impedance of the cone makes it almost hard as rock compared to air. That's the reason we see efficiency levels around 1% only. > Other factors come into play as well. Please tell. best regards Peter > > If your equations take into account the inertia of the speaker cone and the > > fact that it isn't rigidly attached to the speaker frame when you're moving [quoted text clipped - 11 lines] > > Please tell. Well, it seems obvious to me, in fact, it seems so obvious that I would have a great deal of trouble explaining it, simply because it seems so obvious. I guess we'll just have to agree to disagree because I'm not about to go through another thousand-post-plus debate on the issue. My postulation is that a good speaker is the acoustic equivalent of a massless diaphragm over a hole in a wall between the musical source and the listener, and since said diaphragm would not produce Doppler shift in the musical waveform, neither would the speaker. This isn't to say that a speaker, even a very good one, doesn't introduce distortion of several kinds, it's just that none of them are Doppler-related. If you can prove that said diaphragm would introduce Doppler shift, be my guest, but it seems obvious to me that since the hole in the wall doesn't introduce Doppler shift, neither would a massless diaphragm that followed the signal exactly and reproduced the wave perfectly. Introducing mass, nonlinearity, etc, to the diaphragm would add distortion components, but they would not be Doppler-related, so neither would any of the distortion added by a real-world speaker. > Well, it seems obvious to me, in fact, it seems so obvious that I would > have a great deal of trouble explaining it, simply because it seems so > obvious. I guess we'll just have to agree to disagree because I'm not about > to go through another thousand-post-plus debate on the issue. It might be difficult when we both want the last word ;-) But, beware of the obvious. Many silly things have been obvious to many persons through history. > My postulation is that a good speaker is the acoustic equivalent of a > massless diaphragm over a hole in a wall between the musical source and the > listener, and since said diaphragm would not produce Doppler shift in the > musical waveform, neither would the speaker. This isn't to say that a > speaker, even a very good one, doesn't introduce distortion of several > kinds, it's just that none of them are Doppler-related. I can follow your logic. However, the mass-less diaphragm do not reproduce the sound pressure in the hole in the wall, and the loudspeaker does not produce sound pressure off a fixed position. > If you can prove that said diaphragm would introduce Doppler shift, be my > guest, but it seems obvious to me that since the hole in the wall doesn't [quoted text clipped - 3 lines] > they would not be Doppler-related, so neither would any of the distortion > added by a real-world speaker. I am not talking about non-linearities. And that is the exact reason I wanted you to explain the difference in actual diaphragm movement between the Ghost's experiment and the cone reproducing the two frequencies. Peter > I am not talking about non-linearities. And that is the exact reason I > wanted you to explain the difference in actual diaphragm movement > between the Ghost's experiment and the cone reproducing the two frequencies. > > Peter Now, that's actually simple. The ghost's experiment represents the whistle-on-the-moving-train analogy, and the cone reproducing two frequencies represents the diaphragm-over-the-hole-in-the-wall analogy. As for the difference between the two analogies, you either see it or you don't, and if you don't see it, chances are that you won't be able to come up with the necessary equations to prove that they are two totally different phenomena. In summary, the whistle on the train analogy produces Doppler shift, and the diaphragm over the hole in the wall doesn't. If you want the last word, you're welcome to it, just don't phrase it in the form of a queation, so I don't feel the need to answer, :-) > Now, that's actually simple. The ghost's experiment represents the > whistle-on-the-moving-train analogy, and the cone reproducing two [quoted text clipped - 3 lines] > up with the necessary equations to prove that they are two totally different > phenomena. That does not explain the diaphragm motions. > In summary, the whistle on the train analogy produces Doppler shift, and > the diaphragm over the hole in the wall doesn't. > If you want the last word, you're welcome to it, just don't phrase it in > the form of a queation, so I don't feel the need to answer, :-) The above is not a question ;-) In reality I don't expect you to answer, as you have refrained from doing the mathematical analysis a long time ago. I had hoped for Bob Cain og somebody else to come forward. Peter > Ghosts don't have souls, because ghosts don't exist. Pigs have > brains, > ghosts don't, because if the ghost doesn't exist neither does its > brain.. Pigs may die, but ghosts, being nonexistant, never live at > all. At least pigs are good for something. Ghosts are totally useless! Have another drink and a long nap, and get back to us on this when you capable of being even marginally coherent. > > Ghosts don't have souls, because ghosts don't exist. Pigs have > > brains, [quoted text clipped - 4 lines] > Have another drink and a long nap, and get back to us on this when you > capable of being even marginally coherent. My coherency isn't the issue, it's really your lack of comprehension. *Yawn* It's obvious that any entertainment value your posts might have had is long gone, this has become boring, time to put you back in the killfile. Bye, now! >> > Ghosts don't have souls, because ghosts don't exist. Pigs have >> > brains, [quoted text clipped - 11 lines] > had is long gone, this has become boring, time to put you back in the > killfile. Bye, now! This became boring when your killfile stopped working. Since you are a swine and can't avoid your innate mud-slinging temptation, a working killfile is your only hope. On 3/31/05 10:14 AM, in article Xns962A49C827DA8theghosthotmailcom@140.99.99.130, "The Ghost" <theghost@sbcglobal.net> wrote: > This became boring when your killfile stopped working. Since you are a > swine and can't avoid your innate mud-slinging temptation, a working > killfile is your only hope. > Actually this -started out- being boring when somebody added tangential uninterested newsgroups to the destination header. Only takes a second to clean that up... Thanks > On 3/31/05 10:14 AM, in article > Xns962A49C827DA8theghosthotmailcom@140.99.99.130, "The Ghost" [quoted text clipped - 9 lines] > Only takes a second to clean that up... > Thanks And it only takes a second to add me to your killfile. >> > Mike, I only know when this psychopath has thrown more venom >> > my way when others respond to it. [quoted text clipped - 10 lines] > insult someone's intelligence, the very least you can do is try not to > appear illiterate. If I did that, then you wouldn't have anything to criticize; and we certainly wouldn't want that, particularly in view of the fact that you are a self-admitted, technically-inept looser, with limited formal education, a failed marriage, and no noteworthy accomplishments to date. BTW, anyone else notice that Bozo here forced replies offlist to his personal email. Just a little security note as most of us with more than a cell or two firing probably don;t WANT certain classes to have a line on our email... Guy's cute, ain;t he! ALSO, NB: kill those crossposts, don;t know which of the remaining ones WANT this sort of drivel but I figure they'll remove theirs and he'll beleft standing where he belongs. onward: On 4/17/05 8:38 PM, in article Xns963BB38F3B796theghosthotmailcom@140.99.99.130, "The Ghost" <theghost@sbcglobal.net> wrote: >>> In addition to being a technically-inpet fraud and liar, Bob Cain is >>> the consummate hypocrite and a contemptable piece of human waste. [quoted text clipped - 11 lines] > certainly wouldn't want that, particularly in view of the fact that you are > a self-admitted, technically-inept looser, What? He can't untie knots? >with limited formal education, I only had to wear coat-n-tie for 4 years in HS, if that qualifies as formal then I'm limited too, but it isn;t really formal so I guess I haven't had ANY. What school requiers this? > failed marriage, I hadn't heard. Tell! >and no noteworthy accomplishments to date. Now there's a real stumper... what's 'noteworthy' mean here, as somebody who's barely capable of writing in a 4th-grade style and level who manages to post this stuff in NG's where real HS and college grads hang might consider themselves noteworthy, whereas if they were actually all growed up then it wouldn't be noteworthy. Need some background here. Just did so, but everyone should remember not to quote this guy when those who haven't PLONKed him yet so that his diatribes of vast intelligence don't get through. SignatureRoger W. Norman SirMusic Studio http://blogs.salon.com/0004478/ > Mike, I only know when this psychopath has thrown more venom > my way when others respond to it. I have him globally kill > filed and I would urge you to do the same. > > Bob > Just did so, but everyone should remember not to quote this guy when > those who haven't PLONKed him yet so that his diatribes of vast > intelligence don't get through. By all means, and in particular to make even more room for your diatribes of vast intelligence. Thanks for the tip, Bob. Ron > > But ... I suppose I could make an aluminum diaphragm and bolt it onto a > > ring in some way. Now there's a thought. [quoted text clipped - 14 lines] > > A. Einstein >>>So I'd like to use a ring, which is much more compact. But how do > you [quoted text clipped - 5 lines] > Offhand, if there's something you don't see being done by anybody, > there's inevitably a reason why it doesn't work. Well, I see that the d31 of Terfenol-D is about half of the d33 [1]. So Terfenol-D should make a pretty good ring resonator. I don't know about other magnetostrictive materials. I still don't understand why you couldn't just glue your diaphragm to the ID of the magnetostrictive ring. I have examples in my office of pistons glued to the end of Terfenol-D cylinders, and that works. If you can design the diaphragm properly for the piezoelectric case, you should be able to design it for a magnetostrictive driver. [1] http://ieeexplore.ieee.org/iel5/58/27882/01244738.pdf?arnumber=1244738 SignatureDave > >>>So I'd like to use a ring, which is much more compact. But how do > > you [quoted text clipped - 15 lines] > can design the diaphragm properly for the piezoelectric case, you should > be able to design it for a magnetostrictive driver. Ahh, but the thing with cylinders is that they function in an axial (longitudinal) mode and, as you so rightly say, are pistons. But a ring is a different animal because it produces sound in radial mode; a diaphragm stuck in the middle of a ring won't-- can't-- push air like a piston. That's why the mounting of a ring is a trickier proposition than rods and cylinders; for example, the windings on a ring need to move to allow for radial expansion. The advantage of a ring, though, is that it's a bit more compact than a rod or tube, though I'm not wedded to the idea. If a better design option comes along, I'd consider it. :-) Ron >> I was looking over a PDF file I came across on magnetostrictive >> materials, and in particular, Terfenol, too >> get as much as 200 dB of sound using a rod of Terfenol in a Tonpilz >> design. > That's probably in water. snip......snip It is in water and the reference for the quoted 200dB SPL is 1uPa See: http://www.mecheng.osu.edu/~dapino/article.pdf In order to estimate the SPL that the transducer would produce in air, one has to make an assumption about the change in mechanical Q, which is certainly going to increase when the transducer is used in air. Assuming a change in Q of 30, the transducer would be expected to produce 133dB SPL (re 20uP), which respectable but not extraordinary, especially considering that it is a resonant and not a broadband transducer. > My screwdriver worked pretty well using a standard Radio Shack piezo > "buzzer." Despite what people may say, it is possible to get 143 dB > using a piezo transducer-- if it's driven at 200 or 300 volts. To get 143 dB, you need to be very near the transducer > I was looking over a PDF file I came across on magnetostrictive > materials, and in particular, Terfenol, too Yes > get as much as 200 dB of sound using a rod of Terfenol in a Tonpilz 196 dB is max in air at sea level (15 psi). Units for under water are different, where the atmospheric max numerically is in the 200's (like meters vs inches) > design. But my problem is that I am space-limited > and can't use a rod more than an inch or an inch and a half > long, which would have a much higher than 15 kHz resonant frequency. You need a resonator with bends... a tuning fork for instance. > So I'd like to use a ring, which is much more compact. But how do you > attach a diaphragm onto a ring to couple the > ring to the air? There, lies my dilemma. Forget the ring. better yet, saw a notch in it. Now you have a tuning fork! Angelo Campanella > > My screwdriver worked pretty well using a standard Radio Shack piezo > > "buzzer." Despite what people may say, it is possible to get 143 dB [quoted text clipped - 12 lines] > different, where the atmospheric max numerically is in the 200's (like > meters vs inches) < |
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