The inverse square law

• The intensity of an isotropic sound wave decreases as the square of the distance from its source
• Since intensity is proportional to the square of the amplitude, the amplitude of a sound wave decreases as the inverse of the distance from its source
• Close to their source, sound waves are best described as spherical waves with a decreasing amplitude
• Far from their source, sound waves may be approximated as plane waves with constant amplitude

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