Tidal Effect in Small-Scale Sound Propagation Experiment

Kamimura, Seiji; Ogasawara, Hiroshi; Mori, Koichi; Nakamura, Toshiaki

doi:10.1143/jjap.51.07gg08

Cited by 3 publications

(2 citation statements)

References 25 publications

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“…We confirmed the relation of received amplitude level and tidal changes through the previous experiment in 2006 as in [14]. We described the effect of tidal and temperature changes to the travel time with experimental result and calculation in [15,16]. As this experimental area is very small and there were a lot of surface and bottom reflections, it was impossible to detect the single peak witch indicates the direct path.…”

Section: Introductionsupporting

confidence: 74%

Small scale reciprocal sound propagation analysis in Hashirimizu port

Ogasawara

Kamimura

Mori

et al. 2013

2013 IEEE International Underwater Technology Symposium (UT)

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Small scale reciprocal sound propagation was carried out at Hashirimizu port in front of Tokyo Bay, Japan. A pair of the transducers with the distance about 120 m was set at the bank of the port. The average depth at the area is about 4 m. There were so many surface and bottom reflections. In this study, authors investigate the effects of ocean changes such as temperature, tidal level and current, to the reciprocal sound propagations. The 7th order M-sequence was sent every 5 minutes with carrier frequency of 80 kHz. The travel time mainly varied according to the water temperature. But sometimes, it shifted rapidly which could not be considered the effect of the water temperature. As there was almost 1.5 m depth changes because of the tide, the strength of receiving signals also changed according to the interferences of surface and bottom reflections. The biggest peak of the correlated signal was shifted under the conditions of the depth and temperature. It was also confirmed by calculations by finite-difference time-domain (FDTD) method. Because of these complicated interference, it was difficult to estimate current along the propagation path although it was improved by the peak tracing method. But there is still possibility to monitor water flows with few transducers. This method will be possible to monitor the average changes along the sound propagation area. Moreover, it will enable to monitor more accurate temperature or flow distributions using more transducers to create tomography system in the future.

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Section: Introductionsupporting

confidence: 74%

Small scale reciprocal sound propagation analysis in Hashirimizu port

Ogasawara

Kamimura

Mori

et al. 2013

2013 IEEE International Underwater Technology Symposium (UT)

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“…In the numerical analysis of the sound field, [1][2][3][4][5] especially in three-dimensional sound wave propagation with the finite difference time domain (FDTD) method, [6][7][8][9][10][11][12][13][14] enormous computer resources such as memory storage or calculation time are often required for accurate analysis. To cope with the increase in the required computer resources, two approaches are generally applied; one is the algorithmic approach and the other is the hardware approach.…”

Section: Introductionmentioning

confidence: 99%

Three-Dimensional Sound Field Analysis Using Compact Explicit-Finite Difference Time Domain Method with Graphics Processing Unit Cluster System

Ishii

Tsuchiya

Okubo

2013

Jpn. J. Appl. Phys.

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In this study, the compact explicit-finite difference time domain (CE-FDTD) method is applied to the three-dimensional sound field analysis to reduce computer resources. There are various derivative schemes in the CE-FDTD method. They are first examined theoretically to evaluate the numerical accuracy. As a theoretical result, it is found that the interpolated wide band (IWB) scheme has the widest bandwidth in which the cut-off frequency is in agreement with the Nyquist frequency. The calculation performance is theoretically estimated, then experimentally evaluated with the graphics processing unit cluster system. As a result, it is found that the memory usage of the IWB scheme is less than one-third of that of the standard leapfrog (SLF) scheme to achieve the same cut-off frequency. It is also found that the calculation time of the IWB scheme with the shared memory is about 19% compared with that of the SLF scheme with the graphics processing unit (GPU) cluster system. The impulse response is calculated for a large room with a volume capacity of about 4500 m3 in which the sampling rate was 40 kHz. It is confirmed that the three-dimensional sound field with the natural reverberation can be calculated by the IWB scheme.

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