The speed of sound is defined as the

• A. Number of cycles per second of the vibrating particles
• B. Speed at which the sound wave propagates through the medium
• C. Inverse of the frequency
• D. Speed of vibrating particles in the medium

Answer: (B)

Speed of sound is the velocity at which a pressure disturbance—the sound wave—travels through a medium. It describes how fast the wavefront moves, not how fast individual particles in the medium move. In a sound wave, particles vibrate back and forth, but the wave itself propagates at a separate speed. Frequency tells you how many cycles occur each second (the rate of oscillation), not the wave’s travel speed, and its inverse is the period, the time for one cycle. The medium’s properties—stiffness and density—determine how fast the wave travels, with stiffer and less dense media generally allowing faster propagation. A handy relation is v = fλ, linking speed to how often the wave cycles and how long its wavelength is.