atténuation de propagation

OBS: Des ultrasons dans l'eau.

CONT: The propagation characteristics of ultrasound in sea water and its ultrasonic reflection loss on the sea bottom or on fish schools must be studied for both the design and the practical operation of echo sounders, fish finders ... The propagation attenuation in a direction vertical to the sea surface is the result mainly of spherical divergence, but the attenuation in a horizontal direction is caused partly by absorption as well. This absorption becomes larger at higher frequencies ...