[pianotech] FW: RE: New Ask Physicist question

[Ken & Pat Gerler]

It is easy to determine that is the case if you have an old upright with 
hardly any quality sound from the bass. just press on the bass bridge 
pushing it against the sound board as you strike a string and notice the 
increase volume from the string.

Ken Gerler
----- Original Message ----- 
From: "Delwin D Fandrich" <del at fandrichpiano.com>
To: <pianotech at ptg.org>
Sent: Monday, May 18, 2009 2:15 PM
Subject: Re: [pianotech] FW: RE: New Ask Physicist question


| -----Original Message-----
| From: pianotech-bounces at ptg.org
| [mailto:pianotech-bounces at ptg.org] On Behalf Of Stéphane Collin
| Sent: May 18, 2009 9:05 AM
| To: pianotech at ptg.org
| Subject: Re: [pianotech] FW: RE: New Ask Physicist question
|
|
| - If we talk acoustic pressure level, the one caused by the
| strings is very low, due to small surface of the strings and
| huge short circuit effect of the air surrounding them when
| they move.  The one caused by the driven soundboard is much
| higher, even considering the reduction of kinetic energy
| after its transfer from the strings to the soundboard,
| because of its large surface.  So, one can say that the
| soundboard is an acoustic pressure amplifier of its driving
| strings.  Not ?

No, not. It is not "sound pressure" produced by the vibrating strings that 
is
causing the soundboard to vibrate and produce a greater "sound." It is the
mechanical energy in the strings that is being transformed, or transduced, 
into
sound energy. Mechanical energy (vibrations) is coupled via the bridge to 
the
soundboard assembly where, by the forced motion of the soundboard assembly
(still in the form of mechanical vibrations), sound energy is produced in 
the
surrounding air. Nothing is amplified.

ddf