Piano acoustics

[Richard Moody]

| -------- Original Message --------
| Subject: Re: Piano acoustics
| Date: Tue, 29 Jan 2002 11:40:46 -0500 (EST)
| From: Gabriel Weinreich <weinreic@umich.edu>
| To: Richard Brekne <Richard.Brekne@grieg.uib.no>
|
| Dear Mr. Brekne, in this case the simplest process -- transverse motion
| of  the soundboard -- is also the dominant one. ....... I think you can
| understand it better as the bridge giving rise to standing waves in the
| soundboard which are, in fact, what are called modes of vibration of the
| soundboard.
|
- GW



    I take transverse motion to be the simple up and down movement of the
soundboard rather like the back and forth movement of a loud speaker cone
or headphone diaphram.
    I wish "standing waves" would be better defined, but the interesting
concept is that the soundboard "vibrates in modes".   Modes I take to be
what acousticians call the segments of vibrating string that we call
"partials" to differentiate them from "harmonics".... harmonics being a
tone resulting from a fundamental with "overtones" (harmonics) of perfect
ratios.  Because the string is stiff, we are told, the partials are sharp
from  perfect and this sharpness is called inharmonicity.   Now if the
soundboard is vibrating in modes and it is conceivably stiff therefore
shouldn't it have its own inharmonicity?   So,  does the SB somehow
reproduce the frequency of the string's partials (inharmonicity), or does
the SB vibrating in modes with its own stiffness determine (more or less)
the  inharmonicity of the piano?   ---ric