In the actual situation of measuring the sound environmental systems, it is very often that only the resultant response fluctuation contaminated by the additional noise of arbitrary distribution type can be observed. Furthermore, the observed data is usually given in a sound level form on a dB scale based on the logarithmic type non-linear transformation of sound pressure. Therefore, for the purpose of estimating only the undisturbed objective output response, it is necessary to introduce some skillful estimation method for reasonably removing the effect of the above additional noise. In this paper, first, a mathematical model of arbitrary sound environmental systems is introduced in a simplified form of linear system on an intensity scale, by employing the well-known principle property of energy quantities. Next, some practical estimation method of only the objective output response under the existence of background noise is derived without introducing in advance any artificial error criterion like the well-known least-squares method. Then, based on the expression of the above estimation method, a new prediction method of the output response probability function form for arbitrary sound environmental systems without a background noise is proposed by use of observed data contaminated by a background noise. Finally, the effectiveness of the proposed practical method is partly confirmed experimentally too by applying it to the actual sound insulation system.

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Experimental analyses of low noise driving mechanisms for pulse motors used for paper transport and cutter mechanisms in facsimile machines are presented in two parts. The first study focuses on the noise generation mechanism from one-way clutch gear used for torque transmission switching between document paper transport mechanisms and a recording paper cutter, called “chattering noise.” Unexpected movement of the clutch due to internal friction and subsequent collisions of the gears is found to be the cause for this type of noise. The chattering noise is controlled with a spring-friction damper placed between two clutch gears. The second study focuses on the noise generation mechanism observed for particular pulse intervals when the pulse motor for recording paper transport is driven with a double pulse train. It is found to be the rotational oscillation resonance noise from the pulse motors, and it can be controlled using proper double pulse combination timing.

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When the subjective impressions of traffic noises with the same values of L_Aeq are compared, it is often found that rail noise is judged to be less annoying than road traffic noise or aircraft noise. The present experiments were designed to examine the so-called “railway bonus” in laboratory situations. 15 minute noises which contained several events of road traffic noise and/or rail noise were used and their instantaneous loudness as well as overall loudness were judged by German and Japanese subjects. It was confirmed from the results that there may exist a railway bonus in the judgments of loudness also in laboratory situations. That is, the rail noise was judged to be softer than road traffic noise by the both groups of subjects even if the L_Aeq, values were the same. Possible reasons for the existence of the railway bonus may be the difference in frequency components, frequency of events, subjective meanings, etc. between both sound sources. Further systematical and detailed experiments are needed in order to determine the magnitude of the railway bonus as well as its underlying mechanism.

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An exact solution of a partial differential equation including elastic compliance constant S₅₆', with respect to stress function Ψ has been found for torsional modes of vibration of an arbitrary (singly, doubly, triply) rotated quartz crystal beam with a pair of parallel, free edges. The solution is obtained by relaxing the condition that the edge planes are perpendicular to the main faces of the beam. That is, the edges are off perpendicular by the angle θ=arctan (-S₅₆'/S₅₅'). The exact solution can reduce the difference of the calculatedand measured values of frequency constant for a thickness-to-width ratio. Also, a comparatively large-inclination of the edge cuts is required to reduce the unwanted, complicated mode shapes to simple ones.

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