HOW TO CORRECT THE ACOUSTIC OF DAVIES HALL
@ 1985 The Anstendig Institute
Two
events have corroborated The Anstendig Institute's evaluations of the acoustic
of
The first event was the simulcast of the Wagner
"Ring". The sound technicians, with the aid of sophisticated
sound-analyzing equipment, determined that the sound was best when the curtains
on the side walls were left all the way down. It is thought that these
curtains control the reverberation time, but, more accurately described, they
reduce the amount and strength of the sound reflections in the hall.2
The second event was hearing the orchestra play on a
stage that was set up for a large chorus, i.e., without the shiny
reflective wall that is usually at the back of the stage. Fortunately this
concert, the opening of the 1985 Beethoven Festival, contained both the First
Symphony, which uses only the orchestra, and the Ninth Symphony, for which a
chorus was also onstage. It was, therefore, possible to hear the orchestra
alone, but without the reflecting wall, and to hear the orchestra with the
whole back area filled with the sound-absorbing bodies of the chorus.
The Anstendig Institute has previously claimed that
the major problems of Davies Hall lie in the reflected sound, which is too loud
and too diffused. We considered the highly reflective, erratically shaped wall
around the sides and the back of the stage to be a major factor both in the
sound problems in the auditorium and in the problems the orchestra members have
in hearing themselves onstage, in hearing the sound quality they are
reproducing, and in adjusting their tone-quality to suit the acoustic.3
With the orchestra alone onstage and with the
bleachers for the chorus in place of the reflecting wall, the sound quality in
the hall was enormously improved, even when the orchestra played alone, without
the chorus present. Those bleachers, of course, trap and absorb the sound
instead of reflecting it. There were still problems, but noticeably less of the
usual major irritations (a harshness in equalization and a blurring of textures
due to an emphasis of the overtone structures) which make the sound unpleasant
and keep the listener from hearing the finer interpretive nuances.4
With the chorus in place, the sound improved even more. The differences between
the sound with and without the back wall and with and without the chorus in
place are clear differences that should long ago have been noticed and the
correct conclusions drawn as to the proper way to correct the hall's acoustic.
That those conclusions have not been drawn should be attributed to the fact
that the professional and lay public's concepts of what music should sound like
have been formed by current distortions in sound reproduction, which the sound
of the original Davies Hall mimicked (and which that of the present
"corrected" hall with the stage wall in place continues to mimic).5
Those distortions in sound reproduction, which many
acousticians try to imitate, are mainly an emphasis of the overtone structure
(a massing, or doubling, of the overtones6) and a resulting high
frequency emphasis, particularly in the frequency range from 2000 Hz to 5000-6000
Hz, where human hearing is most sensitive and musical overtones are strongest.
The public has long since become used to this wrong high-frequency emphasis,
which is a problem inherent in all sound-reproduction, and accepted it as
correct. In addition, some acousticians, such as those of Davies Hall, have
been influenced by a special technique in sound reproduction that mistakenly
attempts to mimic the "reverberation" characteristics of a concert
hall by electronically time-delaying the original sound and repeating it a
second time a fraction of a second later. The acousticians who imitate these
electronic techniques purposely make concert halls overly reflective
("reverberant") and then, as in Davies Hall, they provide mechanisms
(hangers, i.e., the above-mentioned curtains) which are supposed to be
able to reduce that reflectancy, which they wrongly think of as reducing
reverberation time. The object is to allow more or less reflection
("reverberation") for different kinds of music and different-sized
groups. What is not understood is that the reflections only blur the sound and
that if the sound is blurred in one kind of music, it will be blurred in all
other types of music as well. It is just more difficult in some kinds of music
to notice what is missing because of the blurring.
That the problems of high frequency emphasis and
reflected sound were substantially reduced at the Beethoven concert shows that
the right procedure for improving the hall would be to change the whole wall
behind and to the side of the orchestra. Since the improvement in the sound
with the chorus present proves that no reflected sound at all is necessary,
that wall should be made of totally sound-absorbing material. The audience
section behind the orchestra should also be treated to eliminate totally all
sound reflections in case it is not filled at some concerts. Probably the back
wall below the organ should also be damped, though some experimentation would
be necessary to determine whether or not that wall should be made totally or
only partially sound absorbent.
Unfortunately, even with the presence of the chorus,
which effectively deadened the whole area behind the orchestra, some basic
problems still remained. There is still the problem of an emphasis of the
overtone structure, particularly in the lower instruments, which blurred some
of the musical textures, and there is still too much reflected sound, which
caused some blurring (most evident in the tympani and bass instruments). The
result was a thickness in the sound from the bass-clef up through middle C and
well into the treble clef and an apparent lack of low bass.
At the second concert of the Beethoven
Festival, without the chorus or bleachers, the sound was again typically bad.
The upper instruments were harsh, the trumpets overbearing, and the lower
instruments blurred by the reflections in the hall (for example, the sound of
the kettledrums was diffuse and without solidity and, when the player tried to
silence the drums, they were still heard, even after his hand was on them. In
the dialogue between winds and strings at the beginning of the Scherzo of the
Second Symphony, the strings were unclear because the reflections of the sound
of the winds were still clearly present.) In the second concert, neither the playing
nor the audience settled down to the same levels of concentration achieved in
the concert with the sound-absorbing chorus and/or bleachers in place, and the
concentration in the first concert could still have been better. Since the
Symphony's new Music Director, Herbert Blomstedt, is a conductor with a highly
refined ear for clear, well-defined, well-balanced textures, the acoustic of
Davies Hall will particularly detract from his interpretations. The acoustical
problems need careful attention if the
Obviously, the blurring due to the
"reverberative" reflections can be helped immediately by lowering the
hangers as far as they will go and leaving them there (as long ago recommended
by The Anstendig Institute). But that is not enough since there is a further
problem of unevenness in the sound quality throughout the hall. The acoustic is
not the same everywhere, with the center orchestra section being one of the
worst since it receives the greatest amount of equally loud reflections from
all sides. Solving this problem would demand the judicious application of more
sound-absorbing materials all around the auditorium. This phase of the
corrections would take some experimentation before the correct amount and
positioning of the materials could be achieved. There is no way to do this
other than by trial and error and with the help of people capable of hearing
the differences, who should be given some training in what to listen for (this
training could be achieved with recordings by using various electronic
techniques to manipulate the sound to mimic the acoustical problems).
The author sat in section K of the 1st Tier for the Beethoven opening,
but a trusted colleague heard a repeat of the concert from the orchestra and
reported the usual problems, particularly a difficulty in hearing the upper
strings. The problems in the orchestra section are mainly due to the way the
front of the stage projects the sound, which seems to be upwards, and due to
the too strong, too erratic, and too diffuse reflections from the reflecting
surfaces in the auditorium itself (walls, undersides of the balconies, etc.).
There are too many convex, i.e. diffusing, surfaces in the hall, including the
reflectors hanging above the stage. Applying sound-absorbing material to damp
the reflections in the auditorium would be an important step towards correcting
the acoustic for the orchestra section, if it can be corrected. A remaining problem
would be that the organ cannot be heard well enough onstage to balance it with
the orchestra in works for organ and orchestra. The balance problem may not be
solvable since the organ projects out over the heads of the orchestra, but
concerts with organ and orchestra could be sacrificed without ruining a concert
season.
The differences in the sound with and without the back
wall and the chorus clearly point the way to a solution to the notorious
problems with the Davies Hall acoustic. Correcting the sound reflection
problems and the overtone emphasis go hand in hand, as the techniques used to
reduce the one automatically reduce the other. As pointed out in previous
papers, the sound in Davies Hall is so loud that it can withstand the reduction
in volume from the sound-absorbing materials and, within reason, the volume of
the sound is not crucial to the musical experience. Reducing the volume level
would also mitigate any remaining problems in the orchestra section, especially
those of equalization, since the ear is more tolerant of bad balances at lower
volume levels. Happily, the intermediate solutions (deadening the walls
surrounding the orchestra and the auditorium behind the orchestra and reducing
reflections in the hall) can be carried out quite easily and at much less
expense and effort than could have been anticipated. These recommended
correction procedures are essentially those already suggested years ago by The
Anstendig Institute before they were corroborated by hearing the improvement of
the sound with a chorus in place. No more time should be lost in making the
necessary changes.
FOOTNOTES
1 The
Anstendig Institute's papers on acoustics explain, in non-technical language
for the layman, the basic fallacies and misunderstandings in the field of
acoustic technology which are causing the epidemic of acoustical failures in
modern concert halls. They also document the original acoustic of Davies Hall
and the various stages of the attempts to correct it. All papers are available
free of charge from the institute.
2 Our
paper "Concert Hall Acoustics" explains
the fallacious thinking with regard to reverberation and reverberation times,
fallacies which stem from the fact that the manner in which sound reflections
are measured gives absolutely no information about what is actually heard.
3 Why the
back wall is a major problem is explained in our paper "An Acoustic Anomaly".
4 The institute's papers on sound-reproduction,
hearing, and acoustics explain how sonic irritations degrade the finer
interpretive nuances when the listener hears them. The papers also explain
equalization, which is the balance of the frequency ranges in relation to each
other.
5 The universal distortions in sound reproduction
(records, broadcast, and sound-reinforcement) are dealt with in the institute's
papers on sound reproduction. Also recommended are the papers "The Disaster in Modern Concert Hall Design"
and "Hearing, Our Conditioned Responses
to Music".
6 See our paper "The
Massing of Overtones in Sound Reproduction".
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