ART + Physics = Beautiful
Music By JAMES GLANZ
seat opera house of the adjacent New National Theater.
Can the sense of acoustic intimacy created by a fine concert
"This hall simply has some of the best acoustics in which I
have ever had the privilege to play," the cellist Yo-Yo Ma
wrote in a commentary on the concert hall that appeared
recently in a technical journal. He said its visual and acoustic
aspects combined in a rare synthesis -- "a miracle," he called it.
hall be measured in how many milliseconds it takes sound
waves to ricochet from the walls and balconies and reach a
listener in the seats? Can a hall's aural warmth be calculated
from how efficiently bass notes rebound from the same
surfaces? Can the prized quality called resonance be estimated
from the rate at which the entire hall fades to silence after a
blast of electronic sound?
More to the point, can an architect rely on studies of these
quantities, using computer calculations and measurements in
scale models, to ensure that a structurally innovative, visually
inspiring design for a new concert hall will be an acoustical
triumph rather than a disaster?
For years, the answer to all these questions seemed to be no -the field of concert hall acoustics has had only spotty success.
But now an unusually intense collaboration between architects
and acousticians has put the science of acoustics to the test,
with two major new successes in Tokyo.
The halls in question are the 1,632-seat concert hall of the
multipurpose complex called Tokyo Opera City, and the 1,810-
Both have architecturally daring designs, yet both have been
praised by musicians who have performed in them.
Miracle or no, this is no small feat. "Going to the Moon is
much simpler as a physics problem," said William J.
Cavanaugh, an acoustician at Cavanaugh Tocci Associates who
consults on both the construction and restoration of concert
halls. In a Moon shot, he said, "you've got one source, you've
got one trajectory that will get you there, and you've got one
'listener,' or destination."
But in a concert hall, the trajectories of the sound waves begin
at any number of places on the stage, bounce in complicated
ways from every cornice and pillar, and reach their ultimate
destinations in hundreds of occupied seats.
The research for the new halls, whose principal architect was
Takahiko Yanagisawa, president of TAK Architects in Tokyo,
may be the most extensive use yet of acoustical measurements
and calculations in efforts to design concert halls that are not
simply copies of great halls of the past.
"If you make a copy of the old, great halls, you'll have a great
hall," said Dr. Leo L. Beranek, an architectural acoustician in
Cambridge, Mass., who was the principal acoustical consultant
for the projects in Tokyo. But the Tokyo concert halls, he said,
"are different in appearance and they have the sound of great
halls."
The research is described in three papers, published earlier this
year in The Journal of the Acoustical Society of America, by
Dr. Beranek and Dr. Takayuki Hidaka, chief researcher of the
Takenaka R & D Institute, which conducted acoustical
measurements and built models. The papers describe how, as
the designs took shape, scientists analyzed and worked to
maintain acoustical variables like reverberation time,
spaciousness and intimacy, each with a precise mathematical
definition and musical meaning.
Without those studies, "you're gambling" on the acoustics, Dr.
Beranek said.
Still, the success of two halls in Tokyo is unlikely to persuade
all critics that the science of concert hall acoustics has finally
arrived. There are still many acousticians who maintain that a
knowledge of the technical issues, while helpful, is less
important than experience and a repertoire of acoustically
successful designs that one can fall back on in a pinch.
"If you know your craft and you know your art," said Russell
Johnson of Artec Consultants, "the math today may not help
you very much. And if you believe some math that's wrong,
you can get into trouble very quickly."
That cautionary note was echoed by Dr. Cyril M. Harris, a
professor emeritus of architecture and electrical engineering at
Columbia University. The purely technical approach "works
much of the time, but sometimes it doesn't, and you don't know
the reason why," he said. "So you get trapped. And you get real
disasters."
Yet both Dr. Harris and Mr. Johnson acknowledged that recent
advances in acoustics could yield crucial clues to designers.
The history of concert hall acoustics is nothing if not
contentious. No single approach, whether based on science,
experience, art or pure intuition, has been without its heralded
successes and unexplained failures.
In a way, in fact, musical styles and performance venues have
engaged in what a biologist might call co-evolution,
developing in ways that were inextricably dependent on each
other.
It is no coincidence that the unhurried, vowel-rich Gregorian
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
be less than 1.5 seconds.
Those close walls also added a sense of acoustical intimacy.
That is, the delay between the arrival of sound directly from the
instruments or voices, and sound reflected off the walls and
other surfaces is slight. The smaller the delay, the greater the
sense of intimacy.
sound created by reflections from those objects, acousticians
agree, prevents a nasty acoustic "hardness" or "glare" that
smooth surfaces can generate. (This diffusion is one
characteristic that still awaits a precise mathematical definition,
being determined for now by visual inspection of the interior.)
Later still, as the Classical style of Haydn and Mozart gave
way to the Romantics, large concert halls with correspondingly
longer reverberation times were built to accommodate both the
music and its growing audience.
Symphony Hall rates a special status in the field, since the
person generally regarded as the first to apply science to
architectural acoustics, the Harvard physicist Wallace Clement
Sabine, consulted in its design. Sabine had just discovered a
crucial formula that relates a hall's reverberation time to a hall's
volume and the amount of sound-absorbing material, like
people and curtains, inside it.
Beethoven's later symphonies were composed "almost as
though he anticipated the large, reverberant halls that would be
built in the next half-century," Dr. Beranek wrote in his book
"Concert and Opera Halls: How They Sound" (Acoustical
Society of America, 1996).
In another biological analogue, poor concert halls often did not
survive the wrecker's ball. In a kind of natural selection, the
best halls of the 19th century were more likely to survive. The
three halls most often cited as models of sonorous pleasure are
the Grosser Musikvereinssaal in Vienna (built in 1870); the
Concertgebouw in Amsterdam (1888), and Symphony Hall in
Boston (1900).
Each of those halls is roughly shoebox shaped, leading to quick
reflections from the fairly close side walls and balconies. Each
has a reverberation time of about two seconds. And each
displays numerous irregularities, like coffered ceilings and
rows of buxom statues on its interior walls. The diffusion of
"He really, literally, put the first numbers to this whole
question," Mr. Cavanaugh said. But reverberation time alone
could not divide the good halls from the bad ones. "Anybody
that was working on it knew there was a lot more to it than one
number." Dr. J. Christopher Jaffe of the Norwalk, Conn., firm
Jaffe Holden Scarbrough Acoustics, who also directs a
program on sonics in architecture at Rensselaer Polytechnic
Institute in Troy, N.Y., said that a more complete translation of
the warm, rich sound of the great 19th-century halls into
scientific terms owed much to the development of fresh
acoustical measures, or "metrics," by Dr. Beranek.
"Leo got the Rosetta Stone to get that traditional sound
developed into reflecting patterns," Dr. Jaffe said. "That gave
the architects some great freedom."
That freedom, he said, is most useful for designs, like those of
the new halls in Tokyo, that do not carefully copy the triedand-true, shoebox-shaped halls.
Like intimacy and reverberation time, the additional metrics
have deceptively simple names like spaciousness, bass ratio,
acoustical texture and clarity. But each has a precise
mathematical meaning that seeks to isolate a specific aspect of
acoustical quality in a hall. In the studies leading up to the
design of the new Tokyo halls, said Dr. Hidaka of the
Takenaka R & D Institute, measurements of those and other
metrics were made in 20 opera houses and 25 symphony halls
in 14 different countries. (While New York's Carnegie Hall is
considered among the world's best, it was not included in the
study because there was no opportunity to make acoustic
measurements there, Dr. Beranek said.)
The idea, Dr. Hidaka said, was to get a quantitative measure of
what made the good halls good and the bad ones bad. For the
studies, his team generally produced a burst of sound from a
12-sided speaker on the stage -- actually a dodecahedron with a
small speaker on each face. Each burst and its acoustic
aftermath was recorded on tiny microphones placed in the ears
of dummies, and in some cases the ears of real people,
scattered around the seats.
The team worked out the value of the various metrics for each
hall by analyzing detailed forms of the sound waves picked up
by the microphones. Intimacy, for example, was defined as the
time delay between the direct arrival of the sound from the
stage and that of the very first reflections, which have
presumably bounced off protruding side balconies.
Bass ratio gauges how efficiently low notes, compared with
middle notes, carom from the walls and other surfaces; a high
bass ratio gives a hall what musicians call warmth.
Spaciousness is an estimate of what fraction of all the sound
bathing a listener has been reflected laterally, from interior
surfaces, as opposed to having arrived straight from the stage.
Dr. Beranek, Dr. Hidaka and their collaborators then compared
those measurements with an acoustic ranking of the halls based
on a survey of conductors and music critics. They found that
the most beloved concert halls had reverberation times near
two seconds, intimacy times of not much more than 20
milliseconds and relatively high bass ratios and spaciousness
factors. Other metrics also took on fairly consistent values in
the best halls.
Because of the need for greater clarity in understanding voices,
the optimum reverberation times for opera houses turned out to
be shorter, around 1.5 seconds.
Then the acousticians turned to large computers that had been
programmed to simulate the acoustics in the basic architectural
designs of Mr. Yanagisawa.
The team eventually built a 10-to-1 scale model of the
proposed designs and made just the same measurements, using
tiny speakers, microphones, and one-inch "heads" of dummy
audience members, all scaled down in proportion to the model.
VINDICATION
Even the wavelengths of the sound in the model measurements
were scaled down.
As a chapter in the fractious history of architectural acoustics,
the success of the new Tokyo concert halls can be seen as a
vindication for Dr. Leo L. Beranek, who received years of
negative publicity after the 1962 opening of New York's
Philharmonic Hall, for which he was principal architectural
consultant. The bad reviews garnered by the hall's acoustics
cast a shadow over the scientific approach to acoustics that he
was then developing.
This work led to numerous adjustments in the original designs,
including changes in the height of the ceiling near the stage in
the concert hall, giving some of the balcony fronts a rakish,
forward slant and adding a special sound-diffusing material to
the pyramidal ceiling.
The reflected wave patterns in the finished Tokyo Opera City
concert hall, wrote the team in one of its papers, "appear to be
closest to those for Boston Symphony Hall." Dr. Hidaka said
acoustic data for the opera house resembled those of the famed
Vienna Staatsoper.
For all the apparent success of the Tokyo projects, Mr.
Yanagisawa emphasized that acoustical studies were far from
the whole story. He believes that his general immersion in the
music of the great halls of the world played as large a role in
his understanding of good acoustics as the results of the
technical work did.
"I believe an excellent hall can only be realized by a design
that assimilates nuances beyond description by scientific data,"
Mr. Yanagisawa said. "The final work is a world of sense
created therefrom."
But in the long run, the message from that failure has been
decidedly mixed. The science was far less developed in those
days, and the architects did not follow many of Dr. Beranek's
suggestions, partly out of financial concerns.
Even after Dr. Cyril M. Harris, now a professor emeritus of
architecture and electrical engineering at Columbia University,
led a complete reconstruction in the 1970's -- when it became
Avery Fisher Hall -- and Russell Johnson, an acoustician at
Artec Consultants, made further adjustments to the stage in the
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.