Which property of a sound wave is most closely related to its perceived loudness

• A. Pitch
• B. Loudness
• C. Wavelength
• D. Speed

Answer: (B)

Loudness is governed by how big the pressure fluctuations of a sound wave are—the amplitude. When a wave has larger amplitude, it carries more energy and pushes on the eardrum more forcefully, so it sounds louder to us. Pitch, wavelength, and speed describe other aspects: pitch comes from frequency (how fast the vibrations occur), wavelength is the spatial distance of one cycle and ties to frequency and the speed of the wave in a medium, and speed is how fast the wave travels through the medium and doesn’t by itself set how loud it sounds. So the term that best matches what we perceive as loudness is loudness itself, since it directly reflects the energy carried by the wave that our ears interpret as volume.