Ask any handful of musicians to list the best halls in the world and you’re almost certain to hear the same places mentioned: Vienna’s Grosser Musikvereinsaal, Amsterdam’s Concertgebouw, Boston’s Symphony Hall, New York’s Carnegie Hall. Ask the same musicians to name their favorite halls, and the list is likely to be all over the map, literally. Sentimental favorites will show up: a college hall, a local church, a chestnut infamous for inadequate or downright lousy acoustics but beloved in its community because it has been there forever. In assessing the factors that comprise superior acoustics for musical performance, it’s a better idea to zero in on the shared qualities of those halls universally admired for their sound.
The classic “shoebox” halls such as those in Vienna and Boston have long been touted for warmth, presence, immediacy, strong bass, good balance, clarity, and envelopment—the buzz words of popular acoustics. They share certain architectural characteristics: narrow width, high ceilings, use of massive materials such as plaster and brick that provide hard, non-absorbent surfaces. If this combination yields such superior results, why not just clone their formulas for new concert halls?
Interior of the Grosser Musikvereinsaal, Vienna, Austria
There are several reasons. Architects want to try new approaches and impose their creative personality on a civic edifice. Acousticians are on a quest for the best possible acoustics for each space they design, incorporating new technology as it evolves. But the most important reason by far is that buildings today must be significantly larger in order to accommodate the same seating capacity. Modern building codes require more generous aisle widths, additional fire exits, and other safety features entailing additional space. In this country, the Americans With Disabilities Act has affected both space allocation and patron amenities. Another factor making today’s halls larger is oversize human beings. (Some of the acousticians call this ‘the fanny factor.’) For example, Boston’s Symphony Hall, with a seating capacity in excess of 2600, would be hard pressed to accommodate more than 1800 seats if constructed in accordance with today’s building codes and standards. To fit in those extra seats, one would have to substantially ‘push out’ the room’s boundaries. The increased size would likely have a significant and adverse impact on the hall’s renowned acoustics.
Architects have collaborated with acousticians for a long while, too often in a supervisory capacity. Only in the last twenty years have acousticians begun to assert themselves as key forces in the design and shape of concert rooms for the best acoustical result, including influence on the hall’s seating capacity.
The Basic Premise
A room’s acoustics are governed by the architectural design of that room because of the physics of sound waves. In an enclosed space, musical sound reflects off surfaces: ceilings, floors, and balconies. Simply put, acoustics is inseparable from architecture.
At its most basic level, sound behaves in the same manner as light, except that it travels much more slowly. When it hits a surface, the angle of incidence equals the angle of reflection. In a concert, most of what we hear is not direct sound (sound coming toward us directly from the source of the music-making), but sound reflected off the room boundaries (walls, ceilings, floors, floors, balcony fronts, etc.).
Beginning in the 1970s, acoustics researchers undertook studies that included the systematic evaluation of listener preferences: what people liked. Rather than limiting observations to data that could be measured in a concert hall with a single microphone, a group based in Göttingen, Germany, invented a method whereby listeners could compare the acoustical quality of different halls. They heard multiple loudspeaker reproduction of music in an anechoic chamber (that is, a room with no reflected sound). The researchers simply asked listeners what was their preference, without requiring them to describe sound. (See Yoichi Ando, Concert Hall Acoustics [Berlin and New York: Springer Verlag, 1985]; see also Manfred R. Schroeder, “Toward better acoustics for concert halls,” Physics Today, October 1980)
A key difference in this new approach was the recognition that the listener can distinguish the direction from which sound emanates. The brain processes the slight differences in sound from each ear to form its subjective impression of music. A single microphone does not. By using listener response instead of microphone response, acoustics researchers established a more direct connection to the way human beings perceive live music. As early as 1966, the German acoustician, Manfred Schroeder, was exploring how sound waves travel in an enclosure with a specific shape and specific materials. In the mid-1980s, he summarized his work in preference studies, concluding:
The greater the dissimilarity between the two ear signals (as one would obtain in old-style narrow halls with high ceilings) the greater the consensus preference. (Manfred R. Schroeder, Foreword to Ando, Concert Hall Acoustics)
Acousticians dubbed this phenomenon interaural (or binaural) dissimilarity. Using the information provided by just one ear, the brain can perceive total sound energy (for example, the loudness of full orchestra), the delay of early sound reflections, and some reverberation. With the input of both ears, the listener can experience envelopment in the sound. (Jens Blauert, Directional Hearing). Binaural hearing makes a difference similar to that between stereophonic and monaural recording.
The difference is analogous to that of seeing with one eye as opposed to two. The addition of the slightly different picture that the second eye provides allows the viewer to ‘construct’ a third dimension: depth perception. Similarly, the second ear lends the listener the aural ‘third dimension’—the sense of being surrounded by sound or enveloped by it. Because ears are situated symmetrically on each side of the human head, the listener receives direct, frontal sound identically in both ears. On the other hand, sound arriving from the listener’s sides, provided by what acousticians call lateral reflections, reaches each ear with slightly different timings and frequency spectra. Those differences enable the brain to construct the sense of envelopment, generating the binaural dissimilarity so desirable for listening to music.
This 1970s research yielded an entirely new approach for analyzing concert listening: the concept that lateral sound reflections arriving at the listener’s ears from left and right give the greatest amount of difference in what each ear hears, which in turn provides a greater sense of being enveloped by the music. Manfred Schroeder showed that narrow rectangular halls provide the intense, early-arriving lateral sound that his studies indicated listeners prefer. In a 1984 paper, the English acoustician Nicholas Edwards showed that fan-shaped halls do not. (“Considering Concert Acoustics and the Shape of Rooms,” Architectural Record August 1984, pp133-137) After years of conjecture, acousticians were finally determining the reasons that fan-shaped halls are almost certainly destined for acoustical failure. At the same time they were beginning to understand why the halls such as Vienna’s Musikvereinsaal, Amsterdam’s Concertgebouw, and Boston’s Symphony Hall were so successful: specifically, their relatively small size, their shape and comparatively narrow width with side balconies, combine to provide strong, early reflections. What remained was to determine other reasons for the success of those halls and also ways in which the known successes could be emulated or improved upon.
From Out of Place: A HyperHistory of the Elusive Acoustics of Concert Hall Venues
By Laurie Shulman
© 2002 NewMusicBox
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