Numerical validation of the low-frequency procedure for façade sound insulation measurement: Verification of applicable room dimensions

In the ISO 16283 series for field measurement of sound insulation, the low-frequency procedure is specified for determining indoor average sound pressure level in rooms below 25 m3, where the sound field is dominated by only a few modes. In our previous study, the validity of the procedure was examined through field measurements of façade sound insulation in a wooden house with a room volume of about 20 m3, and some possible modifications were proposed in the procedure. However, it remains unclear whether those modifications are valid for other rooms with different room dimensions, different building structures, and indoor sound absorption conditions. Specifically, the upper limitation of room volume of 25 m3 specified for the low-frequency procedure has not been fully verified. Therefore, this paper investigates the applicability of the modified procedure through numerical simulations with various room configurations. In the simulations, a vibro-acoustic FEM is employed for a simplified room model on the rigid ground surface, where building components are modeled with plate elements. The results demonstrate the validity of the modified procedure in a wider range of room conditions and clarify the applicable range of room dimensions.