Sound in Feet per Second.

[Delwin D Fandrich]

Barrie,

I can't comment on the specifications given for the other materials, but you might be
interested in the following excerpt taken from the outline of a class that I give from
time to time on the subject of Piano Acoustics -- specifically the acoustics of the piano
soundboard.

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

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Barrie Heaton wrote:

> WOOD.
>
>                  Along Fibre     Across Rings   Along Rings
> Acacia          15,467             4,840             4,436
> Fir                 15,218             4,382             2,572
> Beech            10,965             6,028             4,643
> Oak               12,662             5,036             4,229
> Pine              10,900             4,611              2,605
> Elm               14,639             4,916              3,728
> Sycamore      15,314             4,567              4,142
> Ash               16,677             5,297              2,987
> Elder             15,306             4,491              3,423
> Aspen            16,677             5,297              2,987
> Maple            14,472             5,047              3,401
> Poplar            14,052             4,600              3,444
>
> --
> Barrie Heaton