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The floor impact sound generated in multifamily dwellings frequently has a peak in the low-frequency band (20–30 Hz). Because of that, in order to assess the floor impact sound insulation performance in real-life situations, it is necessary to measure floor impact sound using a standard impact source, with an impact force characteristic corresponding to actual impact sources. However, in the current ISO standards, a ‘‘tapping machine’’ that is light and stiff with a weak impact force is the only one that has been approved as a standard floor impact source, which cannot be considered adequate as a method of measurement in solving problems of floor impact sound. Actual case examples of the measurement of impact force performance of floor impact sources generated in actual housing units are presented in this paper, together with a verification of the usefulness of the heavy floor impact source stipulated by current JIS standards in Japan and a proposal for the introduction of the same impact force characteristics as ISO standards.

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This paper presents the deflection characteristics of electrostatic actuators, which have shape modified electrodes and cantilevers. In order to investigate how to get a large deflection with a low voltage, various structures are examined by a numerical calculation. Maximum deflections, just before a cantilever is pulled into an electrode, are evaluated. The numerical analysis shows that the triangular electrode with a triangular cantilever gives large deflection with a low applied voltage.To realize the triangular cantilever, novel fabrication process by a double exposure method is proposed.The experimental results show that the triangular like cantilevers have excellent performance for deflection characteristics, which agrees well with the calculation results.

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