I am not an acoustician, but I think it is incorrect to consider sound and vibration as two different types of energy. Sound IS vibration. If it were possible to measure the amplitude (displacement, energy) that is concentrated in the string for a given note, then measure the amplitude of the soundboard spreading out from that string movement, then measure the amplitude of the surrounding air molecules from that soundboard movement, I assume we would see a considerable loss of amplitude in each step, because no machine is 100% efficient. If so, here's where terminology becomes the point of confusion -- because of our ear's supreme sensitivity to the air's vibrations, we assume (incorrectly) that the SOUND has been AMPLIFIED, when in fact the vibrational energy has dissipated considerably in each step in the process. Get 100 yards from the piano and see how much more atmospheric conditions have caused it to dissipate. Greg Soule -- (sent from webmail) -------------- Original message ---------------------- From: "Escapement" <escapement at comcast.net> > > Sound is definitely energy. The way I see it: the piano converts > vibrational energy into sound energy and in that way *might* be called a > transducer. But the soundboard, in my view, cannot be isolated as the > transducer. > > Again, as I see it, the mechanical energy of the strings is coupled with the > mechanical energy of the soundboard to make the sound. But they do it > together. It is similar to the speaker as transducer. In the speaker, the > voice coil takes the electrical energy and moves the diaphragm to create > sound. The voice coil and the diaphragm together make up the transducer. > In the piano, the strings are analogous to the voice coil and the soundboard > to the diaphragm. No one would say the speaker's diaphragm is by itself a > transducer-it doesn't convert the electrical signal into sound without the > voice coil. > > The problem I have with "soundboard" as "transducer" is that the soundboard, > itself, isn't changing any energy. It is not turning the mechanical energy, > the vibrations, into sound alone-it is working with the strings to turn the > vibrations into sound. Right, as I see it, we have mechanical energy > (vibrations) in the strings moving to mechanical energy (vibrations) in the > soundboard. > > Though in my mind, it's still a bit of a stretch, I suppose, again, you > could call the strings + soundboard a transducer, but even then, the energy > that excites the strings is so similar to the energy the strings produce, > i.e., mechanical energy, motion energy. To my mind, you might have to go > all the way to the music on the sheet to find a suitable difference in > energy (or information). (And depending on your definition of transducer, > it might work). > > But I don't think I'd argue too much with "piano as transducer" or even > "strings and soundboard as transducer." > But I have to say that I feel, as a new student of piano technology, that > hearing the soundboard should be considered a transducer only confuses me. > It doesn't help me understand how the piano works. Maybe I just don't > understand enough about the piano yet-but I do have an inquiring mind. > > But I think this all started with the idea that the soundboard doesn't > "amplify" the sound. I do certainly agree with that. And that is where > things become interesting. If we agree the soundboard doesn't technically > amplify the sound, where does the sound energy come from? This is where my > understanding tells me *resonance* comes into play. And I don't pretend to > understand all the complexities of resonance. But I do feel that adding > "transducer" to the mix only muddies the waters for me. > > Respectfully, Gary > > > -----Original Message----- > From: caut-bounces at ptg.org [mailto:caut-bounces at ptg.org] On Behalf Of Greg > Soule > Sent: Tuesday, May 12, 2009 9:29 AM > To: caut at ptg.org > Subject: Re: [CAUT] Semantics > > I am usually just a lurker here on CAUT, but allow me to chime in. > > Every standard definition of "transducer" that I looked up puts it in > the context of an electrical system - microphone, loudspeaker, TV > picture tube, etc. Other people here with some background in that > field have echoed this definition of changing one kind of energy into > another (sound or light energy to electrical, etc.). It seems we are > borrowing this term from the field of electrical engineering, but I > still don't see how it applies precisely to the string-to-soundboard > relationship. > > Whether it is the string that is vibrating, or the soundboard, or the > air molecules, it is all vibrational energy. What we call > "sound" (because we have ears) is still vibrational energy of the air > molecules. To me, the string-bridge-soundboard chain could be likened > to the bones of the middle ear, which function as a discrete unit to > transmit the vibrations along the chain (with varying degrees of > efficiency). In the ear, the cochlea is the actual transducer, > changing vibrational energy to electrical nerve impulses. > > In the piano, are some people saying that, because the string and > soundboard are such dissimilar materials, and because the perceived > character, or nature, or volume, of the vibrational energy is so > different between them, that they say the energy is not just > transmitted, but transduced (and definitely not "amplified")? But, it > has not changed types of energy, is still vibrational energy. That is > where I am still confused. David Love asked a good question, "Isn't > there such a thing as a mechanical amplifier?" > > If we want to talk about the transducer in a mechanical system like > the piano, shouldn't we be talking about the action-to-string > relationship, not the string-to-soundboard? > > I think I see my next chapter technical taking shape . . . invite in a > local physicist or acoustician (or whatever) to give us the beef on > this whole topic! > > Greg Soule > Marginal CAUT > CAUT list lurker > PTG Assoc. > > > On May 11, 2009, at 10:52 PM, Fred Sturm wrote: > > > On May 10, 2009, at 2:48 PM, Escapement wrote: > > > >> My understanding of a transducer has always been that it is a > >> device that > >> takes one form of information or energy and converts it into > >> another form. > >> (Like the speaker example given where *electrical current* is > >> converted to > >> physical vibrations through the electromagnetic voice coil). The > >> speaker > >> isn't a transducer because the voice coil vibrates the membrane - > >> it's a > >> transducer because it takes the *electrical current* in the wire and > >> converts it to vibrations *(sound)*. In the same way that a > >> microphone is a > >> transducer because it takes *sound* and converts it to an *electrical > >> signal*. > >> > >> But with the soundboard I don't see this conversion. > > > > After thinking it over, I agree with you on this. A classic series > > of transducers would be a coal fire (heat energy) heating water to > > make steam that is directed at a turbine, causing it to spin > > (mechanical energy), which, by means of magnetic field and copper > > coils makes electric current (electrical energy), which, directed > > through the filament of a light bulb makes light energy (and heat > > energy). All are real conversions to obviously different forms of > > energy. > > With a piano, though, we have the mechanical energy of a finger > > moving a key, which causes a hammer to hit a string and sets it to > > vibrate. Mechanical energy converted to mechanical energy in a > > different form via the action of intermediary mechanical devices. > > The string is coupled to a soundboard, and energy is transferred > > causing the soundboard to vibrate, again a mechanical transfer to a > > mechanical form of energy. The soundboard, having a large surface > > area, and operating in atmosphere, transfers some of its vibrational > > energy to air particles, which oscillate creating waves. This still > > seems like mechanical energy to me. The air oscillations reach an > > ear drum, setting it vibrating. IOW, a whole series of transfers of > > mechanical movement from one device or medium to another. Not being > > versed in physics, I don't know whether there is a difference I am > > missing, but it seems much more like a continuum than any two steps > > in the example above. > > I wonder also about referring to sound as energy. It takes energy > > to make sound happen, so sound can be said to be a manifestation of > > energy. But is sound a "form of energy?" > > Maybe this is too abstruse to worry about, but some of the > > confusion in this discussion seems to come from assumptions like the > > notion that sound is equivalent to energy, and similar analogies > > that maybe aren't actually valid. > > Regards, > > Fred Sturm > > University of New Mexico > > fssturm at unm.edu > > > > >
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