Acoustic refraction parallels optical refraction via material-dependent wave speed

Evidence

If there are no surfaces or reflections of any sort, the specific acoustical impedance is an intrinsic property of the medium, given by the product of the density of the medium ρ0 and the speed of sound in it c; z = ρ0c. — Eric J. Heller, Why You Hear What You Hear- An…, 102 (#expands, via linked claim)

For longitudinal waves in solids, the speed of propagation is only affected by the density and Young’s modulus of the material … 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 (#qualifies, via linked claim)

Categorization

• XREF: connects to: Scintillation is a ubiquitous refraction phenomenon across light and radio waves; A medium’s intrinsic acoustic impedance equals density times sound speed — Eric J. Heller, Why You Hear What You Hear- An…, 102; Sound speed in solids depends only on density and elastic modulus — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 64 (+1 more)

Broader Connections

• A medium’s intrinsic acoustic impedance equals density times sound speed #expands (0.85) — Eric J. Heller, Why You Hear What You Hear- An…, 102
• Higher material density slows sound propagation speed #qualifies (0.80)
• Sound speed in solids depends only on density and elastic modulus #qualifies (0.78) — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 64