I'm waiting for someone to say something about imagining the "ideal banjo". Respectfully, Jeff Jeff Farris Piano Technician School of Music UT Austin jfarris at mail.utexas.edu 512-471-0158 On 5/14/09 1:39 AM, "Ed Sutton" <ed440 at mindspring.com> wrote: > Just think of "transducer" in terms of its simple Latin roots: it "leads > across" power from one system to another system. > > Now, imagine an "ideal banjo," i.e. a membrane with zero impedence, in a > large open space. If you strike the string, all of the energy is immediately > transduced into the air "Pow!" There is no reflection, no period motion. > Eveything is displaced once, and returns to rest as the impulse radiates out > into the atmosphere. There is no "vibration," but there is still > transduction of the energy. > > In the piano and recital hall, there are many impedences which reflect the > motions and form them into standing waves, which we call vibrations, sounds, > overtones and such. It is still transduction. The sound always fades away as > the energy is absorbed by the many resistances in the situation. > > Ed S. > > > ----- Original Message ----- > From: "Greg Soule" <afmamh7 at bellsouth.net> > To: <caut at ptg.org> > Sent: Thursday, May 14, 2009 1:05 AM > Subject: Re: [CAUT] Semantics > > >> Wow, this has been an interesting thread. (some of you probably >> abandoned it long ago) >> >> When I wrote, "I think it is incorrect to consider sound and vibration as >> two different types of energy. Sound IS vibration." I hoped it would >> elicit responses (and I think it did) that would finally clarify to me >> why it is claimed the soundboard is a transducer. The way the term >> "sound" was repeatedly defined simply as "what we hear" I found a >> distraction, because it said nothing to differentiate the types of energy >> found in the string, board, air, etc., which is the key to understanding >> the whole kaboodle. It sounded to me more like some fuzzy philosophical >> tangent on human perception ("If a tree falls in the forest . . ."). >> >> So, bear with me while I lay this all out, and tell me if I'm on track >> here . . . >> >> The energy of the string or soundboard has the characteristic of >> vibrating from a fixed point, and the vibrating body is under tension; >> these factors cause it to want to return to a point of repose. The >> vibration has frequency and amplitude. (Finer points of distinction >> could be made between the ways the string and the board vibrate, but not >> by me.) >> >> Although the vibrational energy imparted to the surrounding air also has >> frequency and amplitude, air is a very different kind of medium because >> air molecules are not anchored to anything. Since the energy has no >> fixed point of vibration, it disperses in all directions like ripples in >> a pond. It is a vibration that leaves its point of origin and never goes >> back unless acted upon by an outside force. This is the critical >> distinction of acoustic energy. Sound IS acoustic energy. >> >> Del Fandrich's illustration brings it home . . . a panel of wood that >> vibrates when struck CREATES acoustical energy in the surrounding air. >> This is a different type of energy than that of the string or soundboard, >> and this is why it is proper to refer to the soundboard as a transducer. >> >> Furthermore, even though the term "transducer" in its most common usage >> is borrowed from electrical engineering, and electrical engineers might >> scratch their heads in confusion when they hear piano technicians use it >> about their pianos, it is indeed the best term to apply to how the energy >> changes between the soundboard and the surrounding air. We use it >> knowingly and confidently. >> >> For further reading class, please see: >> http://www.pianobuilders.com/soundboards.html >> http://en.wikipedia.org/wiki/Sound >> http://en.wikipedia.org/wiki/Acoustics >> http://www.sfu.ca/sonic-studio/handbook/Theme_sound_medium.html >> >> Forgive me for being both dense and persistent, thank you for your >> patience and I respect you all very highly, >> Greg Soule >> (and with a final flourish of self-deprecating humor, he returned to join >> all the other lurkers) >
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