Comparison of outdoor microphone locations for measuring sound insulation of building facades

Measurement of the acoustical insulation of building facades requires simultaneous measurement of sound pressure levels indoors and outdoors, but there is still some question as to the best location for the outdoor microphone. This paper reports the differences between sound pressure levels at 2 m from a facade and at its surface, for a series of measurements at 33 different houses. The mean results compare well with a modified line source model, and suggest that a 3 dB correction between measurement locations is appropriate on average, except at low frequencies. The variation in the results, from house to house, suggests that establishing a single preferred outdoor microphone location is desirable.