Acoustic evaluation of orchestra occupancies in concert halls: Effect of sound absorption by orchestra members on audience acoustics

This study investigated changes in the reverberation time at concert hall seats due to the sound absorption of orchestra musicians. Different percentages of musician-occupied areas and densities of the musicians were analyzed on the stages of two 1:10 scale concert hall models. Increasing numbers of musicians was associated with a significant increase in the early-to-late sound index and a significant decrease in the reverberation time at the seats. The effects of volume and absorption coefficients associated with the presence of musicians were investigated in simple computer simulations of shoebox and fan-shaped halls. The results revealed that changes in the orchestra absorption ratio had a greater effect on the reverberation time at the seats than that of the total sound absorption. Therefore, for any given number of musicians in the scale model, the reverberation time at the seats decreased as the percentage of the stage area occupied by the orchestra increased. The reverberation time decreased by more than 0.5 s when the occupied area reached 90%. Furthermore, computer simulations of 12 concert halls showed that the reverberation time at the seats varied in relation to the orchestra absorption ratio.