A medium’s intrinsic acoustic impedance equals density times sound 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

Categorization

• DEFINE: Core definition tethering impedance to intrinsic medium properties when no boundaries exist.
• corroborated: 3 independent passages support this claim — Eric J. Heller, Why You Hear What You Hear- An…, 102
• XREF: connects to: Mass dominates impedance at high frequencies, stiffness at low frequencies — Eric J. Heller, Why You Hear What You Hear- An…, 87; Impedance equals applied force divided by attained velocity; Air transmits sound efficiently because adjacent air cells are impedance matched (+10 more)

Broader Connections

• Sound pressure and intensity relate through air impedance of roughly 415 rayls #exemplifies (0.95)
• Higher material density slows sound propagation speed #complicates (0.90)
• Acoustic impedance mismatch determines both reflection phase and magnitude #expands (0.90)
• Sound speed in solids depends only on density and elastic modulus #complicates (0.85) — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 64
• Sound propagation can be modeled as coupled masses and springs #exemplifies (0.80) — David Howard, Jamie Angus, coustics and Psychoacoustics, 25