The amplitude of sound waves is measured in the units of

The amplitude of a sound wave represents the maximum displacement of particles from their equilibrium position. However, in acoustics, sound is a longitudinal wave characterized by alternating regions of compression and rarefaction. Consequently, amplitude is most commonly measured and expressed as the variation in pressure. The pressure amplitude (Δp) is defined as half the difference between the maximum and minimum pressure within the wave. While amplitude can technically be measured as particle displacement (distance) or velocity, pressure is the standard unit because it is what human ears and microphones primarily detect. The SI unit for this pressure amplitude is the pascal (Pa) or newton per square meter (N/m²). Therefore, among the given options, pressure is the physical quantity used to measure the amplitude of sound waves in practical and scientific contexts.