No abstract

A vibroacoustic numerical method employing an implicit finite-difference time-domain (FDTD) method, in which the target architecture is modeled as a composition of two-dimensional plate elements, is proposed in this paper. While structure-borne sound is a difficult phenomenon to predict owing to the complexity of the vibration mechanism on the building structure, wave-based numerical techniques may enable its accurate prediction by virtue of their flexibility from the viewpoint of modeling the object. However, with the current PC performance, prediction for a large-scale problem is still difficult. To solve such a problem, we model the target structure as a composition of plate elements to reduce the simulated field to two dimensions, in contrast to the discretization of the field into three-dimensional solid elements. This results in memorysaving and faster simulation. In this paper, the basic theory of vibroacoustic analysis for a model with plate elements is described, and the results of a case study for a box-type structure are discussed.

A prediction method for the sound insulation of walls by vibro-acoustical numerical analysis using the finite-difference time-domain (FDTD) method is described. In order to accurately predict the sound insulation performance of walls, numerical modeling of the vibration energy loss of walls in the vibration analysis is necessary. In this study, the energy loss at the boundary part of the plates and the internal damping of the plates are modeled and the sound transmission loss of glass plates and plasterboard walls is calculated. A reasonable agreement is found between the calculation and measurement results and the applicability of the numerical analysis is confirmed.

A vibroacoustic numerical method employing a finite-difference time-domain (FDTD) method, in which the target floor structure consisting of a floor panel supported by support legs on a floor slab is modeled as a composition of two-dimensional plate elements for the double plate structure and one-dimensional bar elements for the support legs, is proposed. While floor impact sound is difficult to accurately predict owing to the complexity of the vibroacoustic mechanism influenced by the coupling phenomena with the vibration of the double-plate structure connected by support legs and the sandwiched air layer between the double plates. In this paper, the basic theory of the proposed numerical scheme was validated through comparison with excitation test on an acrylic scale model, and the applicability of the method to a practical case of a vibroacoustic transmission via a two-layered floor structure was discussed through a numerical case study.

To realize three-dimensional sound reproduction using a bone-conducted sound reproduction device, the effect of the contact condition between the actuator of the bone-conducted device and the surface of each part of the face on the sound localization performance of binaural sound signals reproduced by the device via bone conduction was investigated. As a result of a subjective evaluation experiment, it was found that the sound localization performance of bone-conducted binaural sound was increased owing to the contact force and position of the actuator device.

No abstract

The sound insulation performance of such wall systems as window sashes, doors, and movable partition walls is often affected by sound waves propagating through narrow gaps that exist at their peripheral parts. In this paper, the leak transmission characteristics through narrow gaps existing in the window sash was investigated through numerical and experimental studies. First, the validity of the finite-difference time-domain (FDTD) method with nonuniform-mesh system was confirmed through 1-dimensional and 2-dimensional numerical studies. Second, narrow gaps at the peripheral parts of a window sash were numerically modeled and their leak transmission characteristics were calculated by the 3-dimensional FDTD method. To evaluate the calculation results, they were compared with measurement results of leak transmission characteristics of a real window sash. As a result, numerical results showed good agreement with the experimental results.

Due to limitations of computers, prediction of structure-borne sound remains difficult for large-scale problems. Herein a prediction method for low-frequency structure-borne sound transmissions on concrete structures using the finite-difference time-domain scheme is proposed. The target structure is modeled as a composition of multiple plate elements to reduce the dimensions of the simulated vibration field from three-dimensional discretization by solid elements to two-dimensional discretization. This scheme reduces both the calculation time and the amount of required memory. To validate the proposed method, the vibration characteristics using the numerical results of the proposed scheme are compared to those measured for a two-level concrete structure. Comparison of the measured and simulated results suggests that the proposed method can be used to simulate real-scale structures.