Which property has the greatest influence on the speed of sound in a medium?

Which property has the greatest influence on the speed of sound in a medium?

• A. Density
• B. Temperature
• C. Viscosity
• D. Stiffness (bulk modulus)

Answer: (D)

Speed of sound in a medium is set by how stiff the material is relative to how much it resists acceleration (its inertia). The fundamental relation c = sqrt(K/ρ) shows this: K is the bulk modulus, a measure of stiffness, and ρ is density. A higher stiffness means stronger restoring forces when a compression occurs, so pressure disturbances move through the material faster. Density acts like inertia, so increasing density lowers speed because more mass per volume has to be moved. Viscosity mainly damps waves and can affect attenuation and dispersion, not the basic propagation speed. Temperature can change both stiffness and density, but the direct, dominant factor among the options is stiffness.

Speed of sound in a medium is set by how stiff the material is relative to how much it resists acceleration (its inertia). The fundamental relation c = sqrt(K/ρ) shows this: K is the bulk modulus, a measure of stiffness, and ρ is density. A higher stiffness means stronger restoring forces when a compression occurs, so pressure disturbances move through the material faster. Density acts like inertia, so increasing density lowers speed because more mass per volume has to be moved. Viscosity mainly damps waves and can affect attenuation and dispersion, not the basic propagation speed. Temperature can change both stiffness and density, but the direct, dominant factor among the options is stiffness.