Improvement of a soundproofing vent hole

In tropical climate countries, the house structure with a vent hole is widely used. The vent hole has a structure that penetrates the house's outer wall, allowing fresh air from outside to enter the room. However, external traffic noise also enters the living spaces through the vents. A novel type of soundproof vent hole unit with both soundproofing and ventilation functions was proposed in previous work. An elliptical cavity was used for this unit, but it is difficult to manufacture an elliptical cavity with a high eccentricity; also, the installation and adjustment work are expected to be difficult. A rectangular cavity with an inlet and outlet in orthogonal planes fitted to the house walls is used in this study to provide soundproofing functionality to the vent hole. First, the generation mechanism of sound pressure components propagating inside the unit was theoretically elucidated using the three-dimensional wave equation. Second, to maximize soundproofing ability, methods for reducing the number of resonances and reducing the effect of higher-order sound pressure components are described.