uwacan.propagation.perkins_cutoff#

perkins_cutoff(water_depth, substrate_compressional_speed=inf, speed_of_sound=1500, mode_order=1)[source]#

Calculate modal cutoff for shallow waters.

For shallow waters, the long distance cutoff describes a frequency below which a specific mode cannot propagate.

Parameters:

water_deptharray_like: The water depth, in meters.
substrate_compressional_speedarray_like: The speed of sound in the seabed, in m/s.
speed_of_soundarray_like, default=1500: The speed of sound in the water, in m/s.
mode_orderarray_like, default=1: Which mode order to evaluate. A mode order of 1 yields the same as cutoff_frequency.

Notes

This is evaluated as [1]:

speed_ratio = speed_of_sound / substrate_compressional_speed
(mode_order - 0.5) * speed_of_sound / (2 * water_depth * (1 - speed_ratio**2)**0.5)

This means that the cutoff frequency goes up for softer substrates, and up for shallower depths, and is higher for higher modes.

References

[1]

F. B. Jensen, Wi. A. Kuperman, M. B. Porter, and H. Schmidt, “Computational Ocean Acoustics”, 2nd ed. Springer New York, 2011. Eq. (2.191).