Towards better predictions of theatre chair absorption using the perimeter-to-area method

The present study investigated factors influencing the precision of the perimeter-to-area (P/A) method for predicting the absorption coefficients of theatre chairs in an auditorium, and proposes guidelines for obtaining more precise predictions. Regression lines were fitted to measurements of the absorption coefficients of blocks of theatre chairs with a range of P/A ratios obtained in full scale and scale model reverberation chambers. The choice of numbers of samples, and sample P/A ratios, influenced the precision of regression lines. Samples should be chosen to include a wide range of P/A values, but should not include cases with only 1 row or only 1 chair in each row of sample blocks of chairs. Including a row space in front of the first row of each block of chairs, when calculating sample perimeters and areas, is more likely to lead to more precise predictions than excluding it. The precision of regression lines was also seen to vary with the type of chair such that low absorption chairs and high absorption chairs tended to have less precise regression results.