Particulars of a transmitted acoustic signal at the shelf of decreasing depth

Abstract

The paper analyzes the experimental data obtained in a comprehensive experiment aimed at identifying the regularities of transmitted hydroacoustic signal transformations at the shelf of decreasing depth. The 33 Hz harmonic hydroacoustic signals were generated at the shelf of the Sea of Japan by a low-frequency source. Distribution of the transmitted energy at vertical sounding from the surface to the bottom was studied at different shelf points with Bruel & Kjaer 8104 hydrophone. At the shore, the transformed seismo-acoustic signals were received by a 52.5 m shore laser strainmeter. The experiments showed that about 22% of the transmitted energy was transformed into the energy of hydroacoustic waves propagating in the water. About 72% of hydroacoustic wave energy, in turn, was transformed into the energy of R-waves, which were registered by the shore laser strainmeter. Other regularities of hydroacoustic signals distribution with 33 Hz frequency over the V-shaped shelf are identified.

Assessment of Risks Induced by Countermining Unexploded Large-Charge Historical Ordnance in a Shallow Water Environment—Part II: Modeling of Seismo-Acoustic Wave Propagation

“…Moreover, in contrast to the Rayleigh wave whose amplitude is maximal below the free surface, the maximal amplitude of the waveform is localized deeper within the sea bottom. The waveform likely corresponds to a Sezawa wave [43], [44]. The presence of the 30-m-deep sedimentary basin seems to favor seismic events with LF contents and long durations.…”

“…Indeed, the thickness of the sedimentary layer together with the bathymetry profile that both vary from the source to the coast greatly influences the wave behavior. In shallow-water waveguides with a sloping bottom, it is well-known that the acoustic modes in water may interact with the interface waves supported by the ocean bottom [43], [44]. Furthermore, depending on whether the source is placed on the sea bottom or in the water layer, the generation of the different types of propagation and the distribution of the associated wave energies may differ.…”

Study of Low-Frequency Hydroacoustic Waves’ Behavior at the Shelf of Decreasing Depth

“…On the shore, the transformed seismoacoustic signals were received by a 52.5 m shore laser strainmeter, which was located at Schultz Cape at a point with coordinates N 42 • 34.798 , E 131 • 09.400 . The operation process of the laser strainmeter is briefly described in [3]. The part of the 52.5 m laser strainmeter (corner reflector) closest to the water was located at a distance of 120 m from the water edge and at an altitude of 67 m above sea level.…”

“…Based on the obtained knowledge, the inverse problem can consequently be solved-the development and creation of transmitting systems in specific frequency ranges oriented at the near-bottom propagation of the signals they generate, which is extremely important when establishing ultra-long-distance communication with bottom observatories and mining complexes. The first similar work carried out with a low-frequency hydroacoustic transmitter, generating signals at a frequency of 33 Hz, made it possible to establish some regularities for this frequency range [3]. However, the question remains-how do the regularities identified in [3] transform when the frequency of the transmitted signal is reduced?…”

“…The first similar work carried out with a low-frequency hydroacoustic transmitter, generating signals at a frequency of 33 Hz, made it possible to establish some regularities for this frequency range [3]. However, the question remains-how do the regularities identified in [3] transform when the frequency of the transmitted signal is reduced? In this paper, we study some peculiarities of the propagation and transformation of hydroacoustic signals at the frequency of 22 Hz at the shelf of decreasing depth.…”