Urethane foam is generally used to reduce noise in automobiles, houses, home appliances, etc. Urethane foam for sound absorption consists of a wall (skeleton) and a cavity (air), and the cavities are connected by holes in the wall, but the structure is very complicated. Generally, the Biot–Allard model is used when calculating the sound absorption characteristics, but the parameters used in the calculation are unlikely to lead to actual material development. Therefore, using a 3-D printer (ProJet MJP 5500X-E manufactured by 3D Systems), we created a model with a simple structure of urethane foam. Create multiple types of shaped objects with spherical cavities with a diameter of several millimeters connected by small cylindrical holes with different sphere diameters and cylinder diameters, and use an acoustic tube to determine the vertical incident sound absorption coefficient (hereinafter referred to as sound absorption coefficient). It was measured. We also created an FE model with the same shape and calculated the sound absorption coefficient. We will introduce the knowledge obtained by the measurement and the comparison between the measurement result and the calculation result. In addition, a parametric study of the skeleton and holes was conducted to investigate their impact on sound absorption rates.
Yoshio Kurosawa (Wed,) studied this question.