Reverberation Times and Early Energies in Philharmonic Hall (New York)

Abstract

The data collected in Philharmonic Hall between May 1963 and October 1964 (before, during, and after alterations) were evaluated according to the method for measuring reverberation times described earlier [M. R. Schroeder, Paper J4, this meeting]. The results reveal nonexponential decays for many parts of the Hall. The initial reverberation time (based on the first 10 dB of the decay) at midfrequencies (500–1000 cps), averaged over 12 positions in the empty Hall, dropped from a value of 1.7 sec before alterations to 1.4 sec after absorptive treatment of the rear walls to reduce echoes. The recent installation of a solid stage enclosure raised the initial reverberation time to 1.6 sec. The final reverberation time, based on later portions of the decay (for example, 5–35 dB) was found to be about 2.0 sec before alterations and 1.85 sec after absorptive treatment of the rear walls. It is noteworthy that even the final reverberation times are lower than those previously attributed to the Hall. Evaluations were also made of the early energy (the energy of the direct sound and that arriving within the following 50 msec). On the main floor of the Hall, the early energy between 100 and 250 cps increased by 8 dB relative to midfrequencies, resulting in a better spectral balance. This improvement can be attributed to the new stage enclosure and to the elimination of the gaps between the ceiling panels.