The unit Hertz measures which property of a sound wave?

• A. Frequency
• B. Amplitude
• C. Speed
• D. Wavelength

Answer: (A)

Hertz is the unit for frequency, indicating how many cycles a wave completes in one second. In a sound wave, that means how many air pressure oscillations occur each second. This frequency is what your ear perceives as pitch—the higher the frequency, the higher the pitch. Other properties use different units: amplitude relates to loudness, speed is how fast the wave travels, and wavelength is the distance between consecutive crests. The relationship v = fλ ties them together, so frequency in hertz directly describes how often the wave repeats per second and thus its pitch.