Recently, new ultrasound imaging methods and new blood flow-metry using higher harmonics components based on nonlinear behavior of microbubble ultrasound contrast agent are studied. These ultrasound diagnostic equipment using with ultrasound contrastagentscan be used to improve the accuracy of blood flow diagnosis and to enhance the image ofabnormal tissue like tumors in the ultrasound diagnostic image. In this paper, the resultsof numerical study on relationship between the ultrasound illuminating condition and higherharmonics components included in scattered wave from free air microbubbles in water isreported to develop such a medical diagnostic equipment using the nonlinear response ofmicrobubble contrast agent. This study is performed for a microbubble with radiuslargerthan 10 [μm] suitable to the contrast agent in artery and for a microbubble withradiussmaller than 10 [μm] suitable to the contrast agent in vein. The nonlinear response of freemicrobubbles with size distribution is also studied concerning with the random spacedistribution.

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This study describes the long range propagation of highway noise under favorable conditionsof generation and propagation. For downward ray bending (temperature inversionand/or downwind propagation) geometrical spreading is principally affected by air absorption. The equivalent absorption coefficient is introduced. Air attenuation of the timeaverage sound level, L_AeqT, is calculated for various weather conditions. Finally, for theweather prevailing in the Kyushu District and the percentage of heavy vehicles k≈0.5 (typical for night hours), we have found a relationship between L_AeqT traffic flow and theperpendicular distance to the highway.

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It is well-known that an absorptive obstacle installed on the edge of a noise barrier improvessound shielding efficiency without increasing the height of the barrier. In the present study, the efficiency of a noise barrier with an acoustically “soft” cylindrical edge is investigated. “Soft” indicates that the sound pressure at the surface is zero. It is dimcult, however, frotraditional materials to achieve a soft surface. It is shown that a “Waterwheel cylinder” approximates a soft surface by both theoretical and experimental analysis in a twodimensionalsound field. The Waterwheel consists of acoustic tubes arranged radially; therefore, the sound pressure at the open ends of the tubes (i.e., the surface sound pressure ofthe Waterwheel) depends on the relation between the depths of the tubes and the soundwavelength. The sound shielding efficiency of a half-plane with the Waterwheel cylinderwas measured using a scale model. The results show an improvement in the noise shieldingefficiency by more than 10 dB in a certain frequency range but, unfortunately, the Waterwheeldecreases the noise shielding efficiency of a barrier in another frequency range. Thenoise shielding efficiency is strongly frequency dependent, as is the surface sound pressure ofthe Waterwheel.

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An acoustic tomography system has been designed with an aim to long-term velocitymeasurement in coastal oceans. In this system, Travel times of sound waves propagatingreciprocally between two acoustic stations are measured accurately by using I kHz pulsesignals from GPS (global positioning system). The S/N ratio of signals received is remarkablyincreased by use of the M sequence (maximum period sequence) and arrayed hydrophones.Beamforming also makes it possible to determine the incident angle of signalsreaching the arrayed hydrophones. This system was successfully applied to a 10-km scalevelocity measurement in the Seto Inland Sea, Japan. Path-averaged velocities estimatedfrom the reciprocal transmission data were in satisfactory agreement with the result of the ADCP (acoustic Doppler current profiler) measurement which had been carried out at thesame site for cross comparison. This study provides us a promising step to the full-scalecoastal tomography experiment, performed by a number of acoustic stations which surroundthe coastal regions such as bays and straits.

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Adaptive algorithms, such as LMS are often used in active noise control systems to updatethe strength of the secondary sources. Generally, the assumption of ‘time invariant system’ is introduced and the convergence behaviour of the algorithm is examined. If we try toapply the active scheme to traffic noise control, however, the time invariant assumption isapparently invalid due to the drastic changes in the primary paths. This paper describespreliminary investigations of such cases i.e., the tracking ability of the adaptive algorithmwith moving primary source. The feedforward structure is assumed in the control system, and the well known multichannel filtered-x LMS is used as an adaptive algorithm. Theconvergence properties are examined in both frequency and time domains. The results ofthe simulations in the frequency domain indicate that the attenuation varies irregularlycompared with the case of a stationary primary source. In the time domain calculation, approximately 2 to 3 dB stable attenuation was obtained, however, an adverse effect was alsoobserved especially when the primary source passed in front of the system.

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We present a new formant-type speech analysis-synthesis-editing system based on the ARX (Auto-Regressive with Exogenous Input) speech production model. One of the key featuresof the proposed system is implementation of the algorithm that automatically estimatesvoicing and unvoiced source parameters as well as formant-antiformant parameters of thesynthesizer directly from a speech utterance. After automatically estimating the parametersfrom the utterance, one can manipulate the estimates using a flexible editing tool that hasbeen developed as a part of the system. Using the parameter values so modified, one cansynthesize speech with various voice qualities. Since the system has been developed on the MS-Windows platform, it is expected to be a useful tool in various areas of speech research.

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