Analysis of Tidal Effect on Reciprocal Sound Propagation in Central Pacific Ocean

Self Cite

A sound propagation experiment in very shallow water was conducted at Hashirimizu port in 2009. We transmitted 5 kHz sinusoidal waves with M-sequence modulation. As a result, we found that the travel time concentrated in two time frames. When comparing the travel time with the tide level, the travel time was dependent on the tide level. In terms of the wave patterns, most of the wave patterns have two peaks. As the tide level changed, the biggest peak switched within two peaks. To discuss this, numerical simulation by finite difference time domain (FDTD) method was carried out. The result agreed with the experimental result. Finally, we changed the material of the quay wall in the FDTD simulation and concluded that the first peak is a multireflected combination wave and the effect of its reflected wave at a quay wall has superiority in the second peak.

Section: Introductionmentioning

confidence: 99%

Tidal Effect in Small-Scale Sound Propagation Experiment

Kamimura

Ogasawara

Mori

et al. 2012

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“…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).…”

Section: Biomedical Ultrasoundmentioning

confidence: 99%

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

Mizutani¹,

Wakatsuki²,

Ebihara³

2016

Self Cite

Measurementthe act of measuring physical properties that we performhas the potential to contribute to the successful advancement of sciences and society. To open doors in physics and other sciences, various measurement methods and related applications have been developed, and ultrasound has remained a useful probe, power source, and interesting measurement object for the past two centuries. In this paper, we first summarize the basic principles of ultrasound from the viewpoint of measurement techniques for readers who just have started studying or are interested in the field of ultrasonic electronics. Moreover, we also introduce recent studiesultrasonic properties of materials, measurement techniques, piezoelectric devices, nonlinear acoustics, biomedical ultrasound, and ocean acousticsand their trends related to measurement techniques in ultrasonic electronics to provide some ideas for related applications.

“…1) Acoustic tomography was advocated as a technique for observing wide-ranging global warming by Munk et al 2) The elevated water temperature in the central Pacific Ocean and research on the sound propagation have recently been reported for this oceanic region. 3,4) Moreover, the rise in the temperature of Lake Biwa and its effect on the ecosystem have also been reported. 5) The rise in the temperature of the lake, the local climatic variation, and their relation to global warming are being monitored continuously.…”

Section: Introductionmentioning

confidence: 97%

Direct In situ Measurements of Sound Speed Profile in Thermocline of Lake: The Example of North Lake Biwa in Autumn 2008

Kitamura

Watanabe

2010

In recent years, the rise in water temperature has had an adverse effect on the ecosystem in Lake Biwa. Thus, it is very important to continuously monitor the water temperature. We previously proposed the use of acoustic tomography to monitor the water temperature in Lake Biwa. In autumn, a thermocline develops in Lake Biwa. During this season, the water temperature changes considerably between the warm surface and the cold bottom of the lake, and a circular current develops when the thermocline is formed. It is necessary to ascertain the relationship between the thermocline and the speed of sound. In this study, to determine the relationship between the speed of sound and the water temperature when a thermocline exists, the speed of sound was measured in the north of the lake in autumn 2008. We report the estimated water temperature and the measured speed of sound in Lake Biwa. The speed of sound measured directly was greater than the calculated value for pure water. The existence of the thermocline was also verified at the same time, in which the water temperature changed by about 7.5 °C from the lake surface to a depth of 20 m. The estimated water temperature of the lake assuming nonsaline water was about 0.2 to about 0.5 °C higher than the measured water temperature. To improve the accuracy of the estimated water temperature, the temperature was corrected using a salinity conversion value, which was calculated from the speed of sound measured in situ. The salinity conversion value was used to estimate the water temperature from the speed of sound measured directly in situ in Lake Biwa within an accuracy of 0.1 °C.