An Ocean Acoustic Tomography System with a 200 Hz Giant Magnetostrictive Source

Nakamura, Toshiaki; Nakano, Iwao; Kaihou, Ieharu

doi:10.1143/jjap.37.3172

Cited by 22 publications

(9 citation statements)

References 2 publications

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“…1) One of the methods used to survey the sea condition includes ocean acoustic tomography. 2,3) Ocean acoustic tomography is a technique for measuring water temperature and current, [4][5][6][7] and the result has been applied to the investigation of noise, fluctuation, and internal waves. 8,9) The physical parameters in the ocean can be measured within the reach of sound waves, and ocean acoustic tomography covers a wide range of 1000 km.…”

Section: Introductionmentioning

confidence: 99%

Tidal Effect in Small-Scale Sound Propagation Experiment

Kamimura

Ogasawara

Mori

et al. 2012

Jpn. J. Appl. Phys.

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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.

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Section: Introductionmentioning

confidence: 99%

Tidal Effect in Small-Scale Sound Propagation Experiment

Kamimura

Ogasawara

Mori

et al. 2012

Jpn. J. Appl. Phys.

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“…In a previous study of ocean acoustic tomography, simultaneous transmissions using multiple M-sequence codes from five transceivers were employed to perform precise measurements of ocean currents. [6][7][8][9][10][11][12][13][14] In this case, overlapping signals with different M-sequence codes were rarely observed.…”

Section: Introductionmentioning

confidence: 88%

Automatic Interference Elimination Algorithm for Ultrasonic Multiple Access Method

Wang

Suginouchi

Hashimoto

et al. 2008

jjap

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Ultrasonic sensing systems are currently used in automobiles and mobile robots. Recently, under conditions of multiple ultrasonic sensing systems operating in a small area, we proposed an ultrasonic multiple access method (UMAM) based on the spectrum-spread technology using M-sequence code. However, the effect of the UMAM depends on the preset threshold level. In this paper, we consider an automatic interference elimination algorithm for UMAM. Under conditions with a known interference-signal ratio, the normalized correlation function between two microphones can be used to investigate the effect of the threshold level in UMAM, and further, the optimal threshold level can be obtained from the maximum value of the normalized correlation function. Using a set of suitable training examples, the approximation function between the optimal threshold and the interference-signal ratio can be obtained. From the experimental results, the automatic interference elimination algorithm is a useful tool.

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“…In a previous study of ocean acoustic tomography, simultaneous transmission using multiple M-sequence codes from five transceivers was employed to perform precise measurements of ocean currents. [6][7][8][9][10][11][12][13][14] In this case, the overlapped signals with different M-sequence codes were rarely observed.…”

Section: Introductionmentioning

confidence: 91%

Development of Ultrasonic Multiple Access Method Based on M-Sequence Code

Wang

Siginouchi

Hashimoto

et al. 2007

jjap

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Sonar systems are currently used in automobiles or mobile robots. When multiple active sonar systems operate in a small area, ultrasonic interference is a serious problem. In this paper, we propose an ultrasonic multiple access method (UMAM), in order to realize aerial active sonar systems that can operate in an interference environment. From experimental results, the proposed UMAM was shown to be useful for a highly precise measurement in such an interference environment.

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An Ocean Acoustic Tomography System with a 200 Hz Giant Magnetostrictive Source

Cited by 22 publications

References 2 publications

Tidal Effect in Small-Scale Sound Propagation Experiment

Tidal Effect in Small-Scale Sound Propagation Experiment

Automatic Interference Elimination Algorithm for Ultrasonic Multiple Access Method

Development of Ultrasonic Multiple Access Method Based on M-Sequence Code

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