Shift of the interference extrema of low-frequency acoustic propagations near the axis of a deep sound channel

Abstract

Broadband interference patterns measured from acoustic propagations near the axis of a deep sound channel are interpreted. Analyses using mode theory for the waveguide with bilinear sound speed profiles show that the increase in sound speed without gradient variation shifts the positions of intensity maxima to higher frequencies in a fixed range whereas the increase in the gradient shifts the maxima to lower frequencies. Analytic results imply that the frequency shift of intensity extrema appearing in the measurements could be explained by the increase in the sound speed gradient above the axis of the deep sound channel.

Introduction of measurement techniques in ultrasonic electronics: Basic principles and recent trends

“…Propagation [449][450][451][452][453][454][455][456][457][458][459][460][461][462][463][464][465][466][467][468] Noise [473][474][475][476][477][478][479] Seafloor=sediment [469][470][471][472] Transducers [529][530][531][532] Positioning=ranging 501,[523][524][525][526][527][528] Acoustic imaging Imaging systems [483][484][485][486] Lenses [487][488][489][490][491]...…”

“…When ultrasound reaches the seabed, scattering and absorption occur, whose profile depends on the roughness and type of material. Hence, the measurement of ultrasound propagation is useful for predicting underwater profiles, such as temperatures, currents, tidal effects, [449][450][451][452][453][454][455][456][457][458][459][460][461][462][463][464][465][466][467][468] and underwater structures. [469][470][471][472] Such measurement has been conducted over large regions of the ocean (e.g., on the order of 100 km).…”