Characterization of façade sound insulation by impulse response measurements for various source position formats: a case study

The sound insulation of a building's façade is important for estimating the indoor levels in relation to the outdoor levels. The measurement of the sound insulation (i.e., outdoor-to-indoor level difference) is significantly affected by the methodology employed. In this study, an impulse response measurement methodology is incorporated, alleviating uncertainties associated with the measurement's chain. The effect of loudspeaker position on sound insulation is investigated with respect to three source position formats (horizontal, inclined, and linear), each consisting of three source positions. The appropriate length of the excitation signal is verified using the impulse-to-noise ratio (INR) indicator. Focusing on the outdoor-to-indoor level differences, corresponding to the energy captured in each external receiver (placed very close to windows) and across all the internal receivers per source position, significant differences were found. This indicates the impact of both the distance and angle of incidence between the outdoor receiver and the sound source position. In terms of the average outdoor-to-indoor level difference among the three source formats, the linear format shows slightly lower values compared to the horizontal and inclination source formats, which are similar to each other, but follows the main trend.