Hi Mark, Whew! There is a lot to sort through here. Will get to it tomorrow or the next day in hopes of satisfactorily answering your questions. NG On Thu, Feb 17, 2011 at 2:34 PM, Mark Schecter <mark at schecterpiano.com> wrote: > Hi, Nick. > > Thanks for presenting this definition, I appreciate it, and I think it is > generally helpful. But I would like to raise some questions about it, in the > interest of clarity. I am not an engineer or physicist, but I am a tech and > musician who's been thinking about these questions for a long time. I > present these thoughts hoping to clarify and improve the usefulness of your > definitions, and I welcome your corrections to any misstatements I might > make, or misconceptions I may be trying to apply. That said, ... > > You say: "... thus in a broad but accurate sense the piano string’s > uncoupled and feeble attempt to excite large zones of air demonstrates a > very low amplitude." > > If I may say, characterizing the string as attempting feebly to excite large > zones of air, puts the emphasis in the wrong place. The string is not > attempting anything, it's just vibrating. That its ability to excite much > vibration in air is small, is true. But coupling it to the soundboard does > not raise the energy level/amplitude of the signal. What such coupling does > do is propagate the vibration to many more air molecules than the string > can, due to the soundboard's much larger surface area. But the energy was > never feeble at all, in fact it was always entirely sufficient to the task. > It just needed to be transferred to a material whose form and structure was > better suited to moving air, in order to transmit that vibrational energy to > the listener's ear as sound. But the basic form of energy, mechanical > vibration, has not changed - only the material or medium through which it is > propagating has changed. (Or so I would assert - is any of this wrong?) > > Later you say: "Any device that converts one form of energy, say > vibrational, to another form of energy, say sound, is a transduction device > or transducer." > > I think this statement obscures the fact that sound already IS vibrational > energy, and therefore there is no transduction needed. The only difference > between vibrating string and vibrating air is in the material that is > vibrating, metal to wood to air to eardrum. What IS needed is efficient > propagation of that vibrational energy, from the source (string) through the > bridge and soundboard into the medium (air) which the soundboard provides. > Of course, the soundboard is temporarily the medium as well, but only as a > link in the mechanical chain from vibrating string to vibrating air to > vibrating eardrum. Thus there is no transduction or change in form of > energy, only a change in the physical characteristics of the vibrating > material or body. (Or am I conflating two actually different forms of > energy? If so, what is the difference?) > > Later yet you say: "We can say that the job of piano sound amplification is > to take the weak vibrational signal of the uncoupled string (low amplitude) > and “boost” it via coupling in order to generate a powerful signal (high > amplitude). It doesn’t matter that additional energy is not present for this > to happen." > > Again, I would say that this mis-characterization as "weak" actually > confuses the issue, as the vibrational signal is inherently as strong as it > needs to be to cause its ultimate intended result, sound. It is only "weak" > in its ability to move air, due to its small surface. When we connect it to > a large surface, voila', without adding energy, we create sound (vibrations > in air) of much larger (apparent) amplitude. I am saying that coupling does > NOT "boost" the signal - it merely broadcasts it much more effectively. > Thus, the soundboard is less like an amplifier, and more like a mechanical > broadcast antenna. > > You go on: "Still, an analog to electrical amplification exists in that a > ppp blow to a key can be barley audible; now add more energy with a fff blow > and we have increased amplitude, hence more amplification with the attendant > volume and power." > > Here, I feel that the analogy to electrical amplification is also confusing > as presented, because amplification takes the SAME signal and makes it > larger, whereas your example contrasts a smaller original signal with a > larger original. This is not analogous, as it happens at the source, not the > broadcast end of the chain. > > I do agree that it's perfectly acceptable to call the soundboard an > amplifier for purposes of explaining to lay customers what it does. > > So, what do you think of these thoughts? > > Thanks, and all the best, > > -Mark Schecter, RPT > > > On 2/17/11 10:05 AM, Nicholas Gravagne wrote: >> >> ENERGY TRANSDUCTION VS SIGNAL AMPLIFICATION >> ,,, a simple statement by >> Nick Gravagne >> Thursday, February 17, 2011 > -- Nick Gravagne, RPT AST Mechanical Engineering
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