Terry, Bruce:
We can argue about whether the soundboard is an amplifier or not, but it doesn't change the laws of physics. Energy in = energy out. Nothing disappears, but energy transfers from one form to another.
The energy that is put into the piano by forcing a felt-covered stick to hit a string is not lost. The energy is dissipated in different ways. If those strings are connected to a larger surface area (soundboard) via bridges and ribs, some of that energy will be dissipated by the movement of the board. Movement of that board excites the air around it. That excited air has absorbed some energy from the board and can be measured as sound pressure. The rest of the energy will be dissipated by heating the wires, some into the wood cabinet, the soundboard itself, etc.
A vibrating string by itself has so little surface area that the amplitude of sound pressure is very small. Building a device (a piano) that has the string energy coupled to a larger surface area that moves a larger amount of air, an increased sound pressure results. The only thing that has changed is that the system has become more efficient in changing the energy of a vibrating string into sound pressure.
If one defines "amplification" as an increase of efficiency in the system, then indeed there is amplification. But that is not the way amplification is defined. We do get more of what we wanted from our vibrating string.by adding a sounding board. But It is technically not "amplified", since the common use of the word "amplify" means that some form of energy has been added to augment the the system.
Now, if you add a microphone, pickup or other electronic device, couple it to the vibrating string, connect it to an amplifier where energy is added from an external source, and then connect a loudspeaker to create sound pressure, you will achieve the same result as adding a soundboard coupled to a vibrating string. Your sound pressure levels are going to increase as you add energy (turn up the volume). It will have, in the strict traditional definition, have been "amplified". Making a system more efficient doen't make it an "amplifier".
If you want to define it differently, you can start a cult.
The horse is now suitably flogged, and is now dead. My condolences.
Paul McCloud
San Diego
----- Original Message -----
From: Bruce Browning
To: pianotech at ptg.org
Sent: 02/16/2011 6:22:58 PM
Subject: Re: [pianotech] CA pinblock with tight bushings?
Terry, I have heard this argument before, and still tend to disagree with you on this.
I believe this to be a mechanical amplifier system, just like the old type phonograph, moving something in a large action, when stimulated by a small action.
Other mechanical amplifiers exist, eg. hydraulic systems, levers, and this should not be excluded from the category of amplifier. In fact the definition of a transducer is slightly incorrect, as, in the case of a soundboard, the amplification is purely physical motion ie. small movement of string to large movement of soundboard. The effect on the air movement (giving your definition of a transducer) is a follow on. In a vacuum the soundboard would still move, with no consequential sound.
Just thinking out loud here, but maybe we could see the soundboard in isolation as a transducer between the mechanical motion and the air, but the soundboard system, incorporating the bridge and strings is definitely an amplifier.
On 17 February 2011 08:06, Terry Farrell <mfarrel2 at tampabay.rr.com> wrote:
No, not pulling your leg here Doug. This has been the subject of a number of threads on this forum. The soundboard is a transducer. All the energy that (does indeed) move the soundboard comes from the vibrating strings. There is no energy added to the system beyond what the strings are able to provide. An amplifier is a device that uses an addition of power (most commonly electricity - such as with a powered speaker) to increase the motion of something and thus increase volume.
The reason you don't hear the vibrating piano string very much without the soundboard is that the surface area of the string is very small and simply cannot move much air. When the string is coupled to the soundboard via the bridge, the string moves the soundboard which has quite a lot of area, and thus the volume is louder than the string by itself. However, it can only be as loud as the string has energy and the soundboard is efficient - no energy is added to the system. And thus the soundboard is a transducer.
A transducer is a device that convert one form of energy into another. In the case of the piano, the soundboard/bridge assembly converts the motion energy of the metal strings into sound energy. Nothing is amplified.
regards
--
Bruce Browning
The Piano Tuner
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://ptg.org/pipermail/pianotech.php/attachments/20110216/63030948/attachment.htm>
This PTG archive page provided courtesy of Moy Piano Service, LLC