Abstract
After the war, there was a general understanding of reverberation time (RT), including how to measure it and its significance, as well as its link to a state of diffusion. Reverberation refers to a property of late sound; there was an appreciation that early sound must be significant, but in what way? Research had begun in the 1950s using simulation systems in anechoic chambers, with the Haas effect of 1951 being the most prominent result. Thiele’s Deutlichkeit, or early energy fraction, was important from 1953 and indirectly found expression in Beranek’s initial time delay gap (ITDG) from 1962. The 1960s produced a possible explanation for RTs in halls being shorter than calculations predicted, the importance of early sound for the sense of reverberation (EDT), the nature of directional sensitivity, conditions for echo disturbance, and the importance of early lateral reflections. Much of the research in the 1960s laid the foundations for research investigating the relative importance of the various subjective effects for concert hall listening. Important concert halls built during the period include Philharmonic Hall, New York (1962); Fairfield Hall, Croydon, London (1962); the Philharmonie, Berlin (1963); and De Doelen Hall, Rotterdam (1966). The parallel-sided halls of the past were rarely copied, however, due to architectural fashion. These various halls will be discussed as they make a fascinating group.
Highlights
Jordan (1969) [19] summarizing these results, proposed that the slope over the first 10 dB be used as a measure of reverberance, expressed as the early decay time (EDT), so that the numerical value would be identical to the reverberation time (RT) for a linear decay
In 1966/7 two publications pointed to the possible value of early reflections from the side: Marshall [22], who referred to the quality as “spatial responsiveness”, observed that the situation of unmasked lateral reflections was present in some concert halls and not others and that the former were preferred
Other plan forms from this period [3] were fan-shaped (Helsinki), elliptical (Christchurch, New Zealand), an elongated hexagon (Sydney), surround sound (Denver), and in-the-round (Utrecht). The logic behind these designs was various: in Helsinki as part of a sequence of fan-shaped halls designed by Alvar Aalto, in Christchurch a hall with large suspended reflectors to provide early lateral reflections and in Sydney responding to constraints imposed by the famous roof shape
Summary
A couple of years ago I was asked to summarize the state of acoustic knowledge in the 1960s, at the time when a famous concert hall was being designed. This was the time when I was beginning my life in acoustics and it seemed that others might be interested in what was happening 50 years ago. There is the interesting question: how would you design a concert hall with this limited information?. For more detail on research activity, Cremer and Müller [1] is an extensive resource. Beranek’s books are comprehensive [2,3]
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