HOW TO CORRECT THE ACOUSTIC OF DAVIES HALL
@ 1985 The Anstendig Institute
events have corroborated The Anstendig Institute's evaluations of the acoustic
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.
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".
The Anstendig Institute is a non-profit, tax-exempt, research institute that was founded to investigate stress-producing vibrational influences in our lives and to pursue research in the fields of sight and sound; to provide material designed to help the public become aware of and understand stressful vibrational influences; to instruct the public in how to improve the quality of vibrational influences in their lives; and to provide research and explanations for a practical understanding of the psychology of seeing and hearing. The institute maintains an outreach program utilizing and demonstrating the results of its research.