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Acoustic Phenomena: The branch of physics which deals with the process of production, transmission and reception of sound  is called acoustics. Pressure Amplitude:  Sound wave is a longitudinal wave. It propagates in a medium in the form of compression and  rarefaction i.e. variation in pressure takes place in the medium during the propagation of sound. So,  sound wave or longitudinal wave is also called a pressure wave. The maximum change in pressure in  the medium during the propagation of longitudinal wave is called pressure amplitude. Expression for Pressure amplitude: Consider a wave propagating through air along positive x-direction. The displacement of the vibrating layer of air can be expressed as; y = asin(𝜔𝑡 − 𝑘𝑥) ……………………….( 1) (where a = displacement amplitude, 𝜔 = angular frequency and k = wave vector or propagation constant.) Consider an infinitely small cylindrical vibrating layer of air of length ∆𝑥 and cross-section area ‘A’. Let the left...