Which property of a sound wave determines how loudly it is perceived

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

Answer: (D)

Loudness comes from how strongly the air particles move as the sound wave passes—the amplitude, or the size of the pressure fluctuations. A bigger amplitude means larger pressure changes, delivering more energy to the ear and making the sound seem louder. In physical terms, the wave’s energy grows with the square of the amplitude, so increasing amplitude makes a sound noticeably louder.

Frequency, which is how often the wave cycles per second, determines pitch—the higher the frequency, the higher the pitch—without inherently changing loudness. Speed is about how fast the wave travels through a medium and depends on the medium’s properties, not on how loud the sound is.