An experimental study on the influence of incident characteristics on sound insulation between rooms: Study on the incident sound field in the insulation performance measurement for partition walls. Part 2

The sound field characteristics due to room modes are considered to have strong influences on the low-frequency sound insulation between rooms in field. In this paper, the sound field analysis using the propagation mode expansion method proposed by the authors was applied to the test rooms where the dwelling rooms and the separating wall of an RC apartment building were reproduced. First, the proposed method was validated through the reconstruction of the expanded sound fields and the measurement of the incident directivity. Next, the comparison of the multiple geometries of the source room with two finishing conditions of the RC separating wall demonstrated the influence of the incident sound field on the sound insulation. The mechanism of the sound insulation between rooms was investigated using the proposed method. For the RC single wall, the sound field analysis showed an influence of mode matching between rooms on the low-frequency transmitted sound. For the composite wall which was composed of the RC separating wall and the additional linings, it was demonstrated that the low-frequency resonance transmission phenomenon is affected by the matching of the oblique incidence resonance frequency of the wall and the incident characteristics.