What determines the speed of sound?

• A. Frequency
• B. Intensity
• C. Attenuation
• D. Medium through which sound wave passes

Answer: (D)

The speed of sound is determined by the properties of the medium it travels through—the stiffness of the medium and its density. In general, a stiffer medium that is less dense allows sound to propagate faster, which is why sound moves fastest in solids like steel, slower in liquids like water, and slowest in gases like air. A common way to think about this is that the speed grows with stiffness and drops with density, captured by relationships such as v ≈ sqrt(B/ρ) for fluids or v ≈ sqrt(E/ρ) for solids, where B is the bulk modulus and E is an elastic modulus. Temperature also matters, especially in gases, because it changes density and elastic properties and thus the speed. The key point is that the medium sets the baseline speed; changing frequency affects pitch and wavelength but not how fast the wave travels in a given medium. Intensity and attenuation describe how much energy the wave carries or loses, not the travel speed.