Oceanic ambient noise was measured at the Ieado Ocean Research Station during several months. And the relationship between ambient noise level and wind speed is investigated at each center frequency of one-third octave band.

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In this study, biological transient noises were measured at Hashirimizu Port in Tokyo Bay. The source positions of individual pulses were also estimated using a pair of a tetrahedron arrays. The estimated source positions were concentrated near the wharf edge. The remarkable difference of the estimated source positions was not observed between spring and autumn. However, the peak-to-peak source level was lower than those of the previous studies.

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We proposed a method for determining accurate acoustical physical constants at wide temperature range by combining the resonance method with the UMS technology taking LTGA single crystal. Obtaining the accurate constants and their temperature coefficients by the UMS technology even for narrow temperature range around room temperature, we demonstrated that we were able to calibrate the resonance method and to conduct more reliable determination of constants.

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Based on the ATRM, an underwater acoustic communication algorithm to cancel crosstalk between multiple receiving locations was developed and demonstrated through a simulation. The developed algorithm can transmit the different symbol sequences independently and simultaneously to different receiver locations. By crosstalk cancellation, the performance was improved significantly due to the improved SNR.

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We developed an evaluation method of T_F for SiO_2 glasses. We clarified that V_1 measurements are extremely useful with a resolution of T_F 0.3-0.4℃, and V_<LSAW> measurements can provide two-dimensional T_F distributions on the specimen surfaces. Glass manufacturers can evaluate T_F of fabricated glass ingots, T_F distributions, and their fabrication processes by this ultrasonic method.

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This paper presents an investigation for ray tracing of Lamb wave utilizing a quantitative laser ultrasound visualization technique (QLUV) and two-dimentional wavefronts model. A novel technique called Lamb wave tomography had been made for image restructuring of the defect region information of specimen, including position, size and shape. Previous researches developed existing algorithm to restructure image in Lamb wave tomography. However these restructured algorithms are susceptible to refraction, strong scattering or abrupt change in the thickness and result inaccurate image reconstruction. This paper employs QLUV as experimental ray tracing method for Lamb wave propagating along samples suffering strong refraction on beam distortions. Based on the experimental ray tracing, the existing algorisms called Vidale's method are shown for comparison with QLUV method.

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This research focused on nondestructive laser ultrasound Technique of thermal aged CF-8 duplex stainless steel treated at 723K for 1200 hours. Laser ultrasound technique (LUT) is employed to measure the behavior of guided wave. Based on experimental data, it shows that the phase velocities of CF-8 duplex stainless steel aged at 723K for 1200 hours is faster than unaged treatment caused by microstructure transformation and make the material strength harder.

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This research focus on exploring the effects moisture absorbed by a layer of hygroscopic film coated on the wedge tip along that anti-symmetric flexural (ASF) modes propagate. A shear wave transducer is applied to measure the signals of wedge wave propagating along the wedge tips. Velocity of the ASF mode is indicated to decrease while the moisture is absorbed by the hygroscopic film. Also, the amount of velocity reduction is indicated to be increasing as the moisture increases. Results of the current research suggest the ASF modes can be a new candidate for the application of acoustic sensor to detect moisture.

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