[pianotech] CA pinblock with tight bushings?

[Terry Farrell]

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.

I'm glad you wrote back and asked the question. Thinking that the  
soundboard acts as an amplifier is a very common assumption and  
mistake. Some years ago I would have thought that way also.

And FWIW, the stereo speakers in my family room have speakers that are  
amplified, but both of them also have a passive radiator (speakers  
without a magnetic coil) - I suppose the passive radiators are  
transducers of sorts. They take air motion from inside the sealed  
enclosure (speaker box) and covert it to sound (but isn't air motion  
within the audio hearing range sound by definition?). Yes? I'm really  
not sure about that one!

Terry Farrell

On Feb 16, 2011, at 2:50 PM, Douglas Gregg wrote:

> Terry, If you don't think the soundboard moves, try putting a paper
> clip on a grand soundboard and watch (and hear) it bounce when you
> play.  You can do the same with an audio speaker cone and it does the
> same thing. It moves back and forth and amplifies the sound. Without
> that the piano sounds dead with very little volume. Or were you just
> pulling my leg.
>
> Doug Gregg
>
> Ya gave me a link, so I had to click on it........
>
> From the "Tuning and Repairs" section of that link: "The soundboard
> is the heart of the piano. SNIP  It moves and amplifies the sound of
> the strings."
>
> Ouch!
>
> Terry Farrell