[pianotech] Soundboard rise/fall theory

[Ryan Sowers]

I tune quite a few p22s in schools. They go out of tune in a very specific
pattern. One interesting phenomonon is that leading up to the treble break
the pitch sometimes will get flatter and flatter, the flattest note being
the last one before the break. The very next note will be quite sharp. The
sharpness then will taper off over the next several notes. Depending on the
time of year, it can be the opposite with notes getting sharper leading up
to the break and then suddenly dropping in pitch.

This tells me that: 1. This can't possible have to do with soundboard
rise/fall.  2. There is some sort of twist happening in the structure, with
the pivot being at the treble strut. How else could flat notes be right next
to sharp notes?

Ryan

On Fri, Apr 2, 2010 at 9:41 AM, Joseph Garrett <joegarrett at earthlink.net>wrote:

>  William said:
>  "This may be the way we've been explaining it for eons, but this theory is
> certainly in question. Read Ron N.'s article in the April 2006 Journal
> which speaks directly to this. More, I believe it was Ric Brekne who wrote
> an article some time back which addressed the concept of pitch change due
> to
> soundboard crown increasing. When he isolated the one variable of rise and
> fall of the soundboard, it was pretty quickly apparent that the amount of
> soundboard rise required to affect a significant pitch change was absurdly
> large. The math just doesn't support the theory that soundboard rise and
> fall is responsible for major pitch changes. It is involved to be sure, but
> is likely not even the major factor. Lot's to chew on, and I apologize in
> advance if I've referenced the wrong author."
>
> William,
> It's not just the soundboard that swells in a higher moisture situation.
> The entire piano swells, which puts stress on the plate and the rest of the
> sound producing body(s). That's the way I tend to envision it. There must
> have been some experiments done by manufacturers some where? Anyone?
> Joe
>
>
> Joe Garrett, R.P.T. (Oregon)
> Captain, Tool Police
> Squares R I
>
>
>
>


-- 
Ryan Sowers, RPT
Puget Sound Chapter
Olympia, WA
www.pianova.net
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