ART + Physics = Beautiful Music by JAMES GLANZ

ART + Physics = Beautiful seat opera house of the adjacent New National Theater. Both have architecturally daring designs, yet both have been Music By JAMES GLANZ praised by musicians who have performed in them.

"This hall simply has some of the best acoustics in which I Can the sense of acoustic intimacy created by a fine concert have ever had the privilege to play," the cellist Yo-Yo Ma hall be measured in how many milliseconds it takes sound wrote in a commentary on the concert hall that appeared waves to ricochet from the walls and balconies and reach a recently in a technical journal. He said its visual and acoustic listener in the seats? Can a hall's aural warmth be calculated aspects combined in a rare synthesis -- "a miracle," he called it. from how efficiently bass notes rebound from the same surfaces? Can the prized quality called resonance be estimated Miracle or no, this is no small feat. "Going to the Moon is from the rate at which the entire hall fades to silence after a much simpler as a physics problem," said William J. blast of electronic sound? Cavanaugh, an acoustician at Cavanaugh Tocci Associates who consults on both the construction and restoration of concert More to the point, can an architect rely on studies of these halls. In a Moon shot, he said, "you've got one source, you've quantities, using computer calculations and measurements in got one trajectory that will get you there, and you've got one scale models, to ensure that a structurally innovative, visually 'listener,' or destination." inspiring design for a new concert hall will be an acoustical triumph rather than a disaster? But in a concert hall, the trajectories of the sound waves begin at any number of places on the stage, bounce in complicated For years, the answer to all these questions seemed to be no -- ways from every cornice and pillar, and reach their ultimate the field of concert hall acoustics has had only spotty success. destinations in hundreds of occupied seats.

But now an unusually intense collaboration between architects The research for the new halls, whose principal architect was and acousticians has put the science of acoustics to the test, Takahiko Yanagisawa, president of TAK Architects in Tokyo, with two major new successes in Tokyo. may be the most extensive use yet of acoustical measurements and calculations in efforts to design concert halls that are not The halls in question are the 1,632-seat concert hall of the simply copies of great halls of the past. multipurpose complex called Tokyo Opera City, and the 1,810- "If you make a copy of the old, great halls, you'll have a great "If you know your craft and you know your art," said Russell hall," said Dr. Leo L. Beranek, an architectural acoustician in Johnson of Artec Consultants, "the math today may not help Cambridge, Mass., who was the principal acoustical consultant you very much. And if you believe some math that's wrong, for the projects in Tokyo. But the Tokyo concert halls, he said, you can get into trouble very quickly." "are different in appearance and they have the sound of great halls." That cautionary note was echoed by Dr. Cyril M. Harris, a professor emeritus of architecture and electrical engineering at The research is described in three papers, published earlier this Columbia University. The purely technical approach "works year in The Journal of the Acoustical Society of America, by much of the time, but sometimes it doesn't, and you don't know Dr. Beranek and Dr. Takayuki Hidaka, chief researcher of the the reason why," he said. "So you get trapped. And you get real Takenaka R & D Institute, which conducted acoustical disasters." measurements and built models. The papers describe how, as the designs took shape, scientists analyzed and worked to Yet both Dr. Harris and Mr. Johnson acknowledged that recent maintain acoustical variables like reverberation time, advances in acoustics could yield crucial clues to designers. spaciousness and intimacy, each with a precise mathematical definition and musical meaning. The history of concert hall acoustics is nothing if not contentious. No single approach, whether based on science, Without those studies, "you're gambling" on the acoustics, Dr. experience, art or pure intuition, has been without its heralded Beranek said. successes and unexplained failures.

Still, the success of two halls in Tokyo is unlikely to persuade In a way, in fact, musical styles and performance venues have all critics that the science of concert hall acoustics has finally engaged in what a biologist might call co-evolution, developing arrived. There are still many acousticians who maintain that a in ways that were inextricably dependent on each other. knowledge of the technical issues, while helpful, is less important than experience and a repertoire of acoustically It is no coincidence that the unhurried, vowel-rich Gregorian successful designs that one can fall back on in a pinch. chants sound best in medieval cathedrals, whose "reverberation time" -- the time it takes a burst of sound to fade away -- is 5 to 10 seconds. Later in musical history, the polyphonic, highly articulated Baroque compositions of Bach, Handel and Vivaldi benefited from being played in relatively small rooms with hard, reflecting walls, in which the reverberation times might has a reverberation time of about two seconds. And each be less than 1.5 seconds. displays numerous irregularities, like coffered ceilings and rows of buxom statues on its interior walls. The diffusion of Those close walls also added a sense of acoustical intimacy. sound created by reflections from those objects, acousticians That is, the delay between the arrival of sound directly from the agree, prevents a nasty acoustic "hardness" or "glare" that instruments or voices, and sound reflected off the walls and smooth surfaces can generate. (This diffusion is one other surfaces is slight. The smaller the delay, the greater the characteristic that still awaits a precise mathematical definition, sense of intimacy. being determined for now by visual inspection of the interior.)

Later still, as the Classical style of Haydn and Mozart gave Symphony Hall rates a special status in the field, since the way to the Romantics, large concert halls with correspondingly person generally regarded as the first to apply science to longer reverberation times were built to accommodate both the architectural acoustics, the Harvard physicist Wallace Clement music and its growing audience. Sabine, consulted in its design. Sabine had just discovered a crucial formula that relates a hall's reverberation time to a hall's Beethoven's later symphonies were composed "almost as volume and the amount of sound-absorbing material, like though he anticipated the large, reverberant halls that would be people and curtains, inside it. built in the next half-century," Dr. Beranek wrote in his book "Concert and Opera Halls: How They Sound" (Acoustical "He really, literally, put the first numbers to this whole Society of America, 1996). question," Mr. Cavanaugh said. But reverberation time alone could not divide the good halls from the bad ones. "Anybody In another biological analogue, poor concert halls often did not that was working on it knew there was a lot more to it than one survive the wrecker's ball. In a kind of natural selection, the number." Dr. J. Christopher Jaffe of the Norwalk, Conn., firm best halls of the 19th century were more likely to survive. The Jaffe Holden Scarbrough Acoustics, who also directs a program three halls most often cited as models of sonorous pleasure are on sonics in architecture at Rensselaer Polytechnic Institute in the Grosser Musikvereinssaal in Vienna (built in 1870); the Troy, N.Y., said that a more complete translation of the warm, Concertgebouw in Amsterdam (1888), and Symphony Hall in rich sound of the great 19th-century halls into scientific terms Boston (1900). owed much to the development of fresh acoustical measures, or "metrics," by Dr. Beranek. Each of those halls is roughly shoebox shaped, leading to quick reflections from the fairly close side walls and balconies. Each "Leo got the Rosetta Stone to get that traditional sound developed into reflecting patterns," Dr. Jaffe said. "That gave hall by analyzing detailed forms of the sound waves picked up the architects some great freedom." by the microphones. Intimacy, for example, was defined as the time delay between the direct arrival of the sound from the That freedom, he said, is most useful for designs, like those of stage and that of the very first reflections, which have the new halls in Tokyo, that do not carefully copy the tried- presumably bounced off protruding side balconies. and-true, shoebox-shaped halls. Bass ratio gauges how efficiently low notes, compared with Like intimacy and reverberation time, the additional metrics middle notes, carom from the walls and other surfaces; a high have deceptively simple names like spaciousness, bass ratio, bass ratio gives a hall what musicians call warmth. acoustical texture and clarity. But each has a precise Spaciousness is an estimate of what fraction of all the sound mathematical meaning that seeks to isolate a specific aspect of bathing a listener has been reflected laterally, from interior acoustical quality in a hall. In the studies leading up to the surfaces, as opposed to having arrived straight from the stage. design of the new Tokyo halls, said Dr. Hidaka of the Takenaka R & D Institute, measurements of those and other Dr. Beranek, Dr. Hidaka and their collaborators then compared metrics were made in 20 opera houses and 25 symphony halls those measurements with an acoustic ranking of the halls based in 14 different countries. (While New York's Carnegie Hall is on a survey of conductors and music critics. They found that considered among the world's best, it was not included in the the most beloved concert halls had reverberation times near study because there was no opportunity to make acoustic two seconds, intimacy times of not much more than 20 measurements there, Dr. Beranek said.) milliseconds and relatively high bass ratios and spaciousness factors. Other metrics also took on fairly consistent values in The idea, Dr. Hidaka said, was to get a quantitative measure of the best halls. what made the good halls good and the bad ones bad. For the studies, his team generally produced a burst of sound from a Because of the need for greater clarity in understanding voices, 12-sided speaker on the stage -- actually a dodecahedron with a the optimum reverberation times for opera houses turned out to small speaker on each face. Each burst and its acoustic be shorter, around 1.5 seconds. aftermath was recorded on tiny microphones placed in the ears of dummies, and in some cases the ears of real people, Then the acousticians turned to large computers that had been scattered around the seats. programmed to simulate the acoustics in the basic architectural designs of Mr. Yanagisawa. The team worked out the value of the various metrics for each The team eventually built a 10-to-1 scale model of the "I believe an excellent hall can only be realized by a design that proposed designs and made just the same measurements, using assimilates nuances beyond description by scientific data," Mr. tiny speakers, microphones, and one-inch "heads" of dummy Yanagisawa said. "The final work is a world of sense created audience members, all scaled down in proportion to the model. therefrom."

Even the wavelengths of the sound in the model measurements VINDICATION were scaled down. As a chapter in the fractious history of architectural acoustics, This work led to numerous adjustments in the original designs, the success of the new Tokyo concert halls can be seen as a including changes in the height of the ceiling near the stage in vindication for Dr. Leo L. Beranek, who received years of the concert hall, giving some of the balcony fronts a rakish, negative publicity after the 1962 opening of New York's forward slant and adding a special sound-diffusing material to Philharmonic Hall, for which he was principal architectural the pyramidal ceiling. consultant. The bad reviews garnered by the hall's acoustics cast a shadow over the scientific approach to acoustics that he was then developing. The reflected wave patterns in the finished Tokyo Opera City concert hall, wrote the team in one of its papers, "appear to be But in the long run, the message from that failure has been closest to those for Boston Symphony Hall." Dr. Hidaka said decidedly mixed. The science was far less developed in those acoustic data for the opera house resembled those of the famed days, and the architects did not follow many of Dr. Beranek's Vienna Staatsoper. suggestions, partly out of financial concerns.

For all the apparent success of the Tokyo projects, Mr. Even after Dr. Cyril M. Harris, now a professor emeritus of Yanagisawa emphasized that acoustical studies were far from architecture and electrical engineering at Columbia University, the whole story. He believes that his general immersion in the led a complete reconstruction in the 1970's -- when it became music of the great halls of the world played as large a role in Avery Fisher Hall -- and Russell Johnson, an acoustician at his understanding of good acoustics as the results of the Artec Consultants, made further adjustments to the stage in the technical work did. 1990's, a kind assessment would say that the hall is still not considered among the world's best acoustically.

"At that point, in a sense, the architects had much more say about things," said Dr. J. Christopher Jaffe, an acoustician. There used to be a feeling, he said, that in acoustics, everybody thinks differently, so none of the recommendations need to be taken seriously. But that attitude has changed, Dr. Jaffe said.

A computer-generated analysis of sound reflecting inside the Tokyo Opera City concert hall, shown at right. Architects and acousticians joined to create an innovative and highly praised hall.