Why does sound travel faster in steel than in air, and what determines the pitch of a sound?

• A. Sound travels faster in air; pitch is determined by speed of sound in the medium
• B. Sound travels faster in steel due to greater stiffness; pitch is determined by amplitude
• C. Sound travels faster in steel due to greater stiffness; pitch is determined by frequency
• D. Sound travels faster in air due to lower density; pitch is determined by wavelength

Answer: (C)

Sound travels faster when a medium is stiffer and, to a lesser extent, when it is less resistant to motion. In steel, the bonds are extremely stiff, so disturbances transfer rapidly through the material. Even though steel is much denser than air, that stiffness dominates, giving a much higher speed of sound in steel than in air. The pitch of a sound, on the other hand, is determined by how often the source vibrates—its frequency. A higher frequency means a higher pitch. The speed of the wave and its frequency are related by v = fλ, so pitch depends on frequency, not on how fast the wave travels or on its amplitude. So the best explanation is that sound travels faster in steel due to greater stiffness, and pitch is determined by frequency.