Uniformity of sound fields in large room volumes for the measurement of façade sound insulation

In some countries, it is necessary to measure sound insulation with large receiving rooms that are currently outside the scope of ISO 16283-3. Façade sound insulation needs to be measured in schools, universities and offices, which often have room volumes greater than 250 m3. In this paper, grid measurements of the sound pressure level are made in a receiving room of about 470 m3 with a non-uniform absorption distribution. This allows an assessment of the spatial variation of sound pressure level when measuring the façade sound insulation, where the façade includes windows with relatively low sound insulation. The results show high sound pressure levels near the windows. This results in standard deviations for the spatial variation in the mid and high-frequency range that are higher than would be expected due to the direct field from these windows.