What is the term for the speed at which sound travels through a medium?

• A. Propagation speed
• B. Frequency
• C. Wavelength
• D. Amplitude

Answer: (A)

The term for the speed at which sound travels through a medium is propagation speed. This is the rate at which the pressure disturbance moves through the material, often called the speed of sound. It depends on the medium’s stiffness (how compressible it is) and density—sound travels faster in stiffer, less dense media (for example, faster in bone than in soft tissue, and much slower in air). A handy relation is v = f × λ, where the speed equals frequency times wavelength; this shows that changing frequency changes wavelength but not the underlying speed for a given medium. Frequency is how often the cycles occur per second, wavelength is the distance per cycle, and amplitude is the wave’s strength.