Acoustical Measurements in Philharmonic Hall (New York)

The acoustics of Philharmonic Hall in New York were evaluated by a new method utilizing a digital computer. Measurements were made before, during, and after a four‐phase alteration program of the Hall. The following quantities were studied: (1) reverberation times based on the earlier and later portions of the decay, (2) energies of the direct sound and of reflections from the suspended ceiling, (3) “early” energies (energies arriving within 50 msec of the direct sound) and “reverberant” energies (arriving after 50 msec), (4) directional distributions of the early energies, (5) ratios of early‐to‐reverberant energies, (6) intensities of reflections from the rear wall, and (7) the over all ambient noise level of the Hall. Reverberation times in the octave band 500–1000 Hz, for the main floor, based on the earlier and later portions of the decay, were found to be 1.9 and 2.1 sec, respectively, for the Hall in its original state. In the present state of the Hall, the main floor has a reverberation time of approximately 1.8 sec for both early and later portions of the decay, thus indicating a more exponential decay process. The early and early‐plus‐reverberant energies on the main floor showed a deficiency at low frequencies before the alterations; now, they have a relatively flat spectrum. For an early state of the Hall, the directional distribution of the early energy was close to that expected for a diffuse sound field on the second terrace, but deficient in lateral reflections on the main floor. For the present state of the Hall, the directional distribution of the early energy is less dependent on position, but there are still relatively more lateral reflections on the second terrace than on the main floor in the midfrequency range (250–1000 Hz).