Science Tutorial: Amplitude (Intensity)
A sound wave’s amplitude relates to changes in pressure. The sound is perceived as louder if the amplitude increases, and softer if the amplitude decreases. This is illustrated below.
The amplitude of a wave is related to the amount of energy it carries. A high amplitude wave carries a large amount of energy; a low amplitude wave carries a small amount of energy. The average amount of energy passing through a unit area per unit of time in a specified direction is called the intensity of the wave. As the amplitude of the sound wave increases, the intensity of the sound increases. Sounds with higher intensities are perceived to be louder. Relative sound intensities are often given in units named decibels (dB).
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