Sound in Feet per Second.

[Delwin D Fandrich]

Hi Doug,

Most of this information can be found in the "Wood Handbook: Wood as an Engineering
Material." This is US Department of Agriculture publication. It's official title is
"Agriculture Handbook #72." Unfortunately, there are several older issues of this book all
published under this same title and number. The one you want is the one published in 1987.
That is the most recent issue that I'm aware of. It should be available from the US
Printing Office.

Del

--------------------------------

Doug Richards wrote:

> Del,
>
> Thanks a bunch for the modulus and density info.  I looked for it a whole
> back and couldn't find it.  Can you tell me what type of wood these numbers
> are for?  I started to do a simple finite element model of a soundboard with
> a 3 string unison to look at how much the board stiffness changes the
> response of the strings...  I need the modulus of both spruce and maple to
> do a more accurate job, but anything you have is better than nothing.
>
> doug richards
> San Jose, CA
>
> > -----Original Message-----
> > From: Delwin D Fandrich [SMTP:pianobuilders@olynet.com]
> > Sent: Thursday, May 28, 1998 1:22 PM
> > To:   pianotech@ptg.org
> > Subject:      Re: Sound in Feet per Second.
> >
>         ...
>
> > THE SPEED OF SOUND (SOS) THROUGH WOOD:
> > The speed of sound through wood is independent of species.
> >   --  It VARIES DIRECTLY - with the square root of the modulus of
> > elasticity (MOE).
> >         (Transverse (radial) MOE can be 1/20 of the longitudinal value,
> > hence, the
> >         speed of sound across grain is 1/3 to 1/5 the longitudinal value.)
> >   --  It VARIES INVERSELY - with the square root of the density of the
> > material.
> >   --  It VARIES WITH - grain direction, or angle.
> >   --  It VARIES INVERSELY - with wood temperature and with moisture
> > content (MC).
> >         Both temperature and MC affect MOE.
> >   --  It VARIES INVERSELY - with both frequency and with the amplitude of
> > vibration.
> >
> > In the piano soundboard the speed of sound in, or through, wood is only
> > important because
> > of its direct effect on wave velocity, hence wave impedance. It is not
> > important in and of
> > itself.
> >
> > A piece of wood with a longitudinal modulus of elasticity (MOE) of
> > 1,800,000 psi and a
> > density of 30 lb/ft3 would have a speed of sound in the longitudinal
> > direction of about
> > 150,000 in/sec. In the transverse direction, its MOE would be about
> > 100,000 psi and the
> > speed of sound would be approximately 35,000 in/sec.
> >
> > Regards,
> >
> > Del
> >
> >