Decibel Levels

[Delwin D Fandrich]

----- Original Message -----
From: "Kevin E. Ramsey" <ramsey@extremezone.com>
To: <pianotech@ptg.org>
Sent: December 30, 2000 6:01 PM
Subject: Re: Decibel Levels


>     Once again, Thanks to Del for the informative post. Concerning the
> loudness of the larger piano, I would have instinctively (intuitively)
> thought that the larger soundboard would have caused a greater volume of
air
> to be displaced, thus creating more "volume". I was under the impression
> that volume and loudness are not necessarily the same thing.
-------------------------------------------------

Kevin,

Only in the very low bass would soundboard size become an issue--or, more
accurately, any lack thereof--and even here soundboard size is adequate in
even the smallest piano sizes. There are other factors that limit the
acoustical power of the piano starting with the hammer/action/key mechanism
and how much energy can be transferred from the pianists fingers to the
various strings.

There is probably some minimum practical size for the piano soundboard, but
the physical characteristics of the piano generally determine its actual
size and, to some degree, its shape. That is, within some limits, it is
generally the requirements of the scale layout that determine the basic
shape and size of the rim and, hence, the soundboard. And these factors
generally ensure that the soundboard size is more than adequate. At least in
the grand, uprights are another issue. Here the maximum soundboard size is
determined by the size--the height and width--of the basic box unless the
designer restricts that size by the use of various cutoff bars as I did with
the Fandrich Vertical. Generally, attempts at making the soundboard larger
by making the grand rim 'fatter' are counterproductive. (I know, this is
difficult to actually prove since it would involve making another, otherwise
identical, piano to use as a direct comparison. Still, from my own
experimental work, I have found this to be generally true.)

If all other factors were exactly the same, your assumption, "the larger
soundboard would have caused a greater volume of air to be displaced," would
be correct. However, the amount of air that can be displaced by a soundboard
is limited by many factors other than simply its size--mostly by its
mobility and by its tendency to distort and break up into various resonances
as its size increases. These issues are determined by the overall design of
the soundboard assembly--the specifics of the bridges and their placement on
the board, the size and shape of the ribs and their placement on the board,
etc. It is also affected by the stringing scale--its overall tension,
backscale configuration, degree of bridge loading, etc. An
appropriately-sized soundboard design takes all of these factors into
consideration. An overly large soundboard will have considerable flexibility
unless it is made extraordinarily stiff. Either extreme presents problems.

The question of volume vs. loudness brings up a whole other issue. Are we
talking about absolute acoustic power as measured by Ron's new toy? Or
power/loudness as perceived by our ears? If the latter, then we have to
consider how our ears detect sound and we have to factor in the shape of the
sound envelope and the harmonic structure of that sound envelope.

Del