The accuracy of the absolute calibration of vibration pickups is discussed. The effect of mounting of the laser interferometer and the vibrator is studied for the two conventional calibration methods, i.e. the fringe counting and disappearance methods. The result shows that it is preferable to mount an interferometer and a vibrator on separate heavy blocks independently for highly accurate calibration. The separate mountings make it possible to calibrate vibration pickups within 0.2% total error. A new calibration method using separate mountings is proposed, and effectiveness of this method is examined by comparing with these two conventional methods. This new method covers a wide frequency range including the frequency ranges of the conventional methods. In addition, phase lag from a vibrating surface to a pickup is measured by this method.

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The echo trace of a single fish is theoretically analyzed. The shape and echo level at each point on the trace are expressed as functions of the target strength, orientation, velocity of the fish, the directivity pattern of transducer, etc. From the theoretical results, we derive estimation methods of the fish target strength, swimming velocity and orientation. These methods are applicable not only to a single-beam echo sounder but also to a dual-beam and a split-beam echo sounders. When the swimming speed of a fish is faster enough than a ship speed or when the split-beam sounder is used, even the tilt angle dependence of the target strength can be observed. We developed a quantitative echo-sounder suitable for the echo-trace analysis. These make it possible to read echo levels and ranges at each point on echo traces. The accuracy and effectiveness of the methods were confirmed by analyzing the echoes of calibrated steel spheres. Field observations on fish were performed and the results were examined.

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Relationship between subjective ratings of health state and railway noise were investigated at fifteen sites in Tokyo. The inquiry was conducted for married women and 830 data were available for analyses. Relationships between subjective ratings of health state and answers to each question on objective disturbance were also ascertained in relation to noise levels. In the results, it was found that subjective ratings of health state were closely correlated to age and noise levels. Greater age and higher noise levels increased ill-health. Annoyance indicated no relation to subjective ratings of health state, whereas sleep disturbance, mental disturbance or physical symptoms indicated close relation to subjective ratings of health state. Noise higher than 70 dB (A) accelerated increase of ill-health. Noise higher than 60 dB (A) indicated increase of highly disturbed respondents to sleep disturbance, mental disturbance and physical symptoms. These results suggested that noise could cause ill-health in the meaning of subjective ratings of health state.

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Ultrasonic velocity and absorption in liquid diiodomethane have been measured in the frequency range 100 MHz-1.7 GHz at the temperatures of 10° and 20°C using the highresolution Bragg reflection method. Vibrational relaxation was observed which was ascribed to all the vibrational modes except the lowest. Vibrational relaxation frequency β in fifteen liquids obtained in our previous and present works is plotted as a function of fundamental vibration frequency ν of the relevant trigger mode. The relation log β=A-kν well fits the data within the factor of two, where A and k are constants. This indicates fundamental vibration frequency is a dominant factor in determining relaxation frequency.

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A general method of predicting a road traffic noise generated from an arbitrary non-Poisson type traffic flow was previously proposed for practical use, based on the information on an elementary response wave form when one vehicle passes directly in front of an observation point. By developing this prediction method, in this report, more advanced investigation applicable to a fairly complicated acoustic environment is described by applying it to the actual road traffic noise observed especially at a T-type road intersection in a city area. At this time, the effects of the surrounding background noises are reasonably taken into account for predicting the road traffic noise.

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