5.30  acoustic propagation constant. Natural logarithm of the complex ratio of the steady-state particle velocities, volume velocities, or pressures at two points separated by unit distance in a uniform system (assumed to be of infinite length), or at two successive corresponding points in a system of recurrent structures (assumed to be of infinite length). The ratio is determined by dividing the value at the point nearer the transmitting end by the corresponding value at the more remote point.

Annotation              In each case, the disturbance is assumed to be a single-frequency progressive wave of small amplitude.

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