Tohru Miyajima

Finite-difference time-domain analysis of the vibration characteristics of building structures using a dimension-reduced model

In order to accurately predict the vibration characteristics of buildings, wave-based numerical methods are effective from the viewpoint of the modeling accuracy of the physical mechanism and the detailed geometries of the simulated field. However, because of the performance of current PCs, the prediction of real-scale problems remains difficult. In order to address such problems, we herein propose a vibration simulation method for a beam-plate structure using a dimension-reduced modeling method. The target structure is modeled as a composite structure consisting of two-dimensional plate elements and one-dimensional beam elements, which are coupled based on the implicit finite-difference approximation scheme. By applying such a low-dimensional element, a faster simulation that requires less memory, as compared with a three-dimensional discretization scheme, is made available. To validate the method, the vibration characteristics obtained by the proposed scheme are compared to the measured results for mode...

The development of an audible simulator of sound fields and verification of simulation accuracy

A multichannel‐type audible simulator with two special features, such as scattering sound and a way to determine production condition of reverberation, is developed. Using geometrical sound analysis with sound‐scattering phenomenon, a sound field model of the simulator is composed of direct sound, initial reflection, reverberation, and scattered sound. Also, a new way to determine the production condition of reverberation is proposed. To examine the similarity between a simulated sound field and a real sound field, physical and psychological experiments are performed. It is found that acoustic indices, such as C80 (clarity), modulation transfer index (MTI), and time gravity (schwerpunktzeit), of simulated sound fields approximately agree qualitatively with those of the real sound field. The results of psychological experiments using dummy head recordings show that definition has good similarity, and it is necessary to improve reverberation.