Wood grain direction changes bending wave speed and radiative efficiency

Evidence

The speed of bending waves in wood sheets depends not only on the frequency, as in glass, but on direction relative to the wood grain. The speed is higher along the grain than perpendicular to it. The critical frequency along the grain for a violin is about 5000 Hz, but for a cello, with its thicker wood, it is about 2800 Hz. Above these frequencies, the instruments become better sound radiators. Violins, piano soundboards, and many other musical instruments can reduce short-circuiting by making the opposing regions (across a nodal line from each other) unmatched—for example, if one region is small and the opposing region is large. Adjustments in structure, shape, or thickness can accomplish this. A violin, for example, breaks symmetry by asymmetrical placement of the bassbar stiffening the top plate and the soundpost that carries vibrations of the bridge to the bottom plate. — Eric J. Heller, Why You Hear What You Hear- An…, 678

Categorization

• XREF: Connects directly to the reader’s trees-as-infrastructure essay (grafting & growth) — wood’s anisotropic acoustic properties as material science backing.
• ADDENDUM: Wood grain anisotropy in acoustic radiation could serve the trees-as-infrastructure essay — how material anisotropy in living/worked wood shapes its uses.