Wood grain direction drastically changes the speed of sound through the material

Evidence

However, although the density of a solid is independent of the direction of propagation in a solid, the Young’s modulus may not be. For example, brass will have a Young’s modulus which is independent of direction because it is homogeneous, whereas wood will have a different Young’s modulus depending on whether it is measured across the grain or with the grain. Thus brass will propagate a disturbance with a velocity which is indepen­ dent of direction, but in wood the velocity will depend on whether the dis­ turbance is traveling with the grain or across it. … This variation of the speed of sound in materials such as wood can affect the acoustics of musical instruments made of wood and has partic­ ular implications for the design of loudspeaker cabinets, which are often made of wood. In general, loudspeaker manufacturers choose processed woods, such as plywood or MDF (medium density fiberboard), which have a Young’s modulus that is independent of direction. — David Howard, Jamie Angus, coustics and Psychoacoustics, 41

However, although the density of a solid is independent of the direction of propagation in a solid, the Young’s modulus may not be. For example, brass will have a Young’s modulus that is independent of direction because it is homogeneous, whereas wood will have a different Young’s modulus depending on whether it is measured across the grain or with the grain. Thus brass will propagate a disturbance with a velocity that is independent of direction, but in wood the velocity will depend on whether the disturbance is traveling with the grain or across it. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 64

Categorization

• XREF: Relates directly to the published article ‘Grafting & Growth: On Trees as Infrastructure’ and to instrument-craft traditions reading wood grain. — connects to: Wood’s anisotropy makes sound radiation direction- and frequency-dependent; Higher material density slows sound propagation speed; Sound speed in solids depends only on density and elastic modulus — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 64 (+1 more)
• SEED: Angle: how material anisotropy shapes craft knowledge across woodworking, instrument building, and cabinet design — the grain people listen to.
• corroborated: 4 independent passages support this claim — David Howard, Jamie Angus, coustics and Psychoacoustics, 41; David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 64

Broader Connections

• Higher material density slows sound propagation speed #expands (0.85)
• Sound speed in solids depends only on density and elastic modulus #contradicts (0.82) — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 64
• Baroque mansions achieved balanced acoustics through wood paneling absorbing low frequencies #exemplifies (0.72)