Which of the following is a measure of the loudness of sound?

The measure of the loudness of sound is related to amplitude. Amplitude refers to the maximum extent of a vibration or oscillation measured from the position of equilibrium. In the context of sound waves, a larger amplitude means that the sound wave carries more energy, producing a louder sound.

When sound waves travel through a medium, they create compressions and rarefactions. The higher the amplitude of these waves, the greater the pressure variations, which our ears perceive as loudness. Therefore, amplitude directly influences how loud or soft a sound is perceived.

In contrast, frequency determines the pitch of the sound rather than its loudness. Energy can influence amplitude, as higher energy levels can produce greater amplitudes, but it is not a direct measure of loudness by itself. Velocity pertains to the speed at which sound travels through a medium and does not affect the loudness of the sound.