NATS 1720 Lecture Notes - Lecture 2: Overpressure, Rarefaction, Longitudinal Wave
19 Oct 2017
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Unit 1 the nature of sound: lecture #2. Note: pressure fluctuations above or below the normal atmospheric pressure correspond to compressions and rarefactions. 1. - in the particle picture (displayed below), a sound wave is an alternating sequence of compressions and refractions. The overpressure in a rarefaction is: positive, negative, zero. The area with less particle density is a low pressure area. This means that the overpressure distortion occurs below the normal level of atmospheric pressure, the normal level of atmospheric pressure being labeled at 0 on a graph. In contrast, the compression area (where particles are more densely located) is a high pressure area and has positive overpressure. a longitudinal wave is a wave where the local disturbance is parallel to the direction of propagation of energy. Overpressure: it measures the change in normal atmospheric pressure by measuring the difference between normal atmospheric pressure and the total pressure in the sound wave.
