Speaker
Description
In this paper, the influence of sample size and mounting conditions on the laboratory measurement of the airborne sound insulation of a monolithic wall of aerated concrete blocks is assessed. The same aerated concrete wall was measured in an accredited laboratory in a full-size test opening of 4.00 m x 3.00 m, according to the ISO 10140 standard series, and also in a reduced-size test opening of 1.62 m x 1.87 m, with deviations from the standard conditions: no ratio of the niche depths of 2:1, and no covering of the cavity with reflecting material. The differences in the resulting sound reduction indices between 200 Hz – 5000 Hz fall between 5 and 10 dB, and 8 dB in the SNQs –all in favour of the smaller sample.To achieve better agreement between the two results, further measurements were carried out on the reduced-size sample after modifying the mounting conditions: the acoustic cavity was covered with sound-reflective material, and a thick wooden frame was installed onto the laboratory wall to restore the 2:1 niche depths ratio.The sound reduction indices were also calculated according to ISO 12354-1 versions 2010 and 2017, with the measured longitudinal velocity [m/s] and the mass [kg/m3] of the blocks. Also the influence of sound absorption in the cavity was analysed by means of numerical simulations. The results of these investigations are summarised.