In this paper we describe a new method of locating sound sources in one dimensional space such as in a tube. Several methods have been proposed up to now to locate sound sources using cross spectral or correlation techniques. It is impossible, however, to locate sound sources by such conventional methods in cases where there is more than one sound source or when there are reflecting points in the tube. Therefore, we propose here a new method of locating sound sources using several sensors. In this method, the position of a sound source is first assumed, and the transfer functions from the assumed sound source to all the sensors are calculated using the sound velocity and the distances between them. After compensating the transfer characteristics, the cross spectra between all the pairs of sensor outputs are averaged. The assumed source point is scanned all over the tube. If the assumed source point coincides with the actual source point, the magnitude of the averaged cross spectrum takes a large value. However, the magnitudeis less if the assumed point does not coincide with the actual point. The usefulness of this method is confirmed by both the computer simulation and the experiments using an electric shaker and a stream of water leaking from a hole in pipe.

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General trends of the target strength of fish or other organisms are investigated by using prolate spheroidal scattering models. The soft spheroid is taken as the model of the swim bladder of fish, and the liquid spheroid for the fish body without bladder. Backscattering amplitudes are calculated for the spheroids with typical physical parameters of actual fish. They are shown as the frequency and size dependences, the backscattering patterns, and the density and sound speed dependences. These results are compared with experimentally observed target strengths of sardine, mackerel, krill, etc. A good agreement was found. The dorsal-aspect target strength of bladder fish shows little frequency dependence and is approximately proportional to the squared body length. Almost all the backscattered energy is attributed to the bladder. The target strength of the fish or organisms without a bladder is very small. Their swimming orientation and physical parameters of the body considerably affect the scattering to cause variability in the target strength.

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A flat wood diaphragm 105×105 mm in size for a low to middle range loudspeaker was developed using the wood for soundboards of musical instruments. It is necessary forthe wood diaphragm to be humidity-proof and isotropic. For the former, coating with varnish, which was the same as that used for the soundboards, and acetylation, which was essential in the conversion of hydrophile property, were carried out. The humidityproof performance of these treatments was tested, and each treatment showed the characteristic effect. For the, latter, rectangular wood bars for reinforcing radial (R) direction, which was lower in strength, were glued to both edges of the square wood board, one side of which was parallel to longitudinal (L) direction, in L direction. It was found that the wood board with the bars, wood diaphragm, had a circle node at quasi-isotropy, and it was clarified that the circle node was produced by the degeneration of both vibrations in each direction of L and R. Loudspeakers with the developed wood diaphragm showed acceptable performance.

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A ceiling design based on the quadratic-residue sequence for enhancing the early lateral reflections is described. The design has a hexagonal star pattern which can blend very well with comtemporary architecture. Measurements confirm the expected excellent scattering pattern over large angles.

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Field measurements were carried out to determine the sound attenuation of ear protectors under conditions of impulsive noise. The sound protection of different types of earplugs and earmuffs was measured for both in single and in combination. The effect of different weapons, different shooting places and shooter positions on the sound attenuation of such ear protectors was also measured.

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In this report, the equivalent expression for the mean value of arbitrary non-linear type state variable with respect to the arbitrary non-Gaussian random phenomena is first derived theoretically by use of the expectation operation based on only the standard Gaussian distribution function. Next, based on this convenient expression, an estimation method of the noise evaluation index, L_e, is newly derived in a hierarchical form containing the well-known usual estimation method derived under the assumption of the standard Gaussian distribution as the first expansion term. That is, this method is generally applicable to any kind of random phenomena by grasping the statistical information on the noise level fluctuation. Finally, the validity of the proposed method is experimentally confirmed too by applying it to the actual road traffic noise data.

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