The speed of sound in a material depends on which properties of the material?

• A. Density and Elasticity of the Material
• B. Color and Temperature
• C. Magnetic Permeability
• D. Electrical Conductivity

Answer: (A)

The speed of sound in a material is determined by how easily the material can be compressed and how much inertia it has. This comes down to density and elasticity: density is a measure of inertia (more massive material resists motion, slowing the wave), while elasticity (stiffness) measures how strongly the material restores itself after being deformed (a stiffer material transmits the wave faster). In simple terms, waves travel faster when the material is stiff and not too heavy, following a relationship that roughly scales with the square root of stiffness divided by density. For common solids, this is often described by v ≈ sqrt(E/ρ) for longitudinal waves, with more complete formulas using bulk and shear moduli for exact cases. Colors or basic temperature aren’t the primary determinants, and magnetic permeability or electrical conductivity don’t set the acoustic speed in typical solids.