10.6.2 Amplitude and intensity of the sound waves

Last updated at July 3, 2026 by

šŸ’” How big, how strong

Amplitude is how far the density swings; intensity is how much energy pours through — together they decide how much punch a sound packs.

What is amplitude?
Amplitude the maximum change in density in a compression or rarefaction compared to the average density; more amplitude means more energy.
  • The maximum change in density (in a compression or rarefaction) compared to the average density.
  • A larger change in density means a larger amplitude (Fig. 10.20).
  • A larger-amplitude wave carries more energy .
What is intensity?
Intensity the sound energy passing through unit area, perpendicular to the wave, in unit time; it falls with distance.
  • The sound energy passing through a unit area, perpendicular to the wave, in unit time.
  • As sound spreads over a larger area with distance, its intensity decreases (energy is conserved).
  • Louder (larger-amplitude) sounds carry more energy and travel farther.
Important Definitions
  • Amplitude — the maximum change in density in a compression or rarefaction compared to the average density.
  • Intensity — the sound energy passing through unit area, perpendicular to the wave, in unit time.
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