Which definition best describes amplitude in a sound wave?

• A. The maximum displacement from the baseline
• B. The time between successive peaks
• C. The number of cycles per second
• D. The distance between peaks

Answer: (A)

Amplitude is how far the wave’s oscillation swings away from its resting value. In a sound wave, that means the maximum deviation of air pressure from ambient pressure. A larger amplitude corresponds to a louder sound because bigger pressure changes carry more energy to our ears. The distance between peaks is the wavelength, the time between peaks is the period, and the number of cycles per second is the frequency—each describes a different aspect of the wave, not how big the oscillation is. So the definition that best describes amplitude is the maximum displacement from the baseline.