4 years ago



DESIGN AND CONSTRUCTION IMPROVING ACOUSTICS IN EXISTING THEATRES Only a Minimum of Treatment and Expense Is Required To Achieve Efficient Acoustics in Older Theatres by ROBERT BOLLER* I HOUCH THE MODERN THEATRE Can be designed to assure perfect acoustics, older houses can be made just as efficient acoustically as the new theatres with a minimum of treatment by means of the excellent acoustical materials available. My knowledge of acoustics has been obtained the hard way, and in many cases we have done a lot of experimenting, sometimes successfully and other times not too good. However, we have learned that the answer to achieving good acoustics in existing theatres is usually much simpler than might be expected, and that the job need not necessarily be expensive. SOUND GAVE THE IMPETUS The greatest study in acoustical correction came in the late 20s with the advent of sound. Many of the older houses in silent days which were designed for the normal spoken voice had bad conditions for high intensity sound. The talking picture demanded correction of these conditions, as in some of these houses it was nearly impossible to understand a single word that was spoken. Then the acoustical expert came into being. Many articles had been written in the architectural magazines, in the years prior to this, by eminent authorities recommending certain shapes and ideal sizes with very little mention of sound ab.sorption—though mention was often made regarding the difference in acoustics in an auditorium when with the conclusion empty and when filled, that the clothing of the patrons made the difference. In most instances, the oval or egg-shaped auditorium was generally recommended as most ideal: as a result, many were built along these lines. I recall one such auditorium that was built in Boston which was considered perfect acoustically. Later, one of a very similar shape was built in Portland, Ore., that had excessive reverberation. So shape alone was not the answer. would often cause confusion directly below the fascia. Also, too high an untreated wall at the rear of the house, especially if curved, could cause confusion. Ceiling beams of excessive depth, untreated, and extreme wall projections also caused considerable confusion. A solution to the untreated balcony fascia was to use ornamental carving or an irregular shape to break up the sound. Today, in new theatres balcony fascia are usually designed straight and treated with acoustical material. VENEERED CHAIRS AT FAULT Many of the older houses, excepting the de luxe type, had veneered chairs with veneered backs, which had no absorption value when empty. Steel ceilings were very common in the older houses and were always considered bad from an acoustical standpoint, and we had always discouraged their use. However, I have had occasions during a remodeling program to observe some of these installations and in some instances the sound was perfect, probably due to the fact that the panels were pressed into a deep ornamental pattern which had a tend?ncy to break up the sound. One of the reasons of the success of good acoustics in some of the older houses also was that they were constructed with wood floors which did have considerable absorption value. In many of the older houses the booth walls were constructed with two inches of solid cement plaster which allowed a maximum amount of transmission thi'ough Ihem. In several instances we were requested by the management to check the house to see what could be done toward correcting the trouble. In one case the manager had been given an excessive bid to correct the fault, which in each case occurred near the booth. Upon investigation we found the projectionist had th? booth monitor turned on loud, transmitting the .sound through the walls to confuse with the horn at the screen. By having the booth walls insulated against .sound, the trouble was economically overcome. One great source of acoustical trouble, often overlooked, occurs at the rear wall of the stage, the sound reverberating throughout the entire house. However, this is generally most noticeable in the firs few rows, depending on the intensity. This is ofti-n noticed in older houses with loft>. where the scenery has been removed, allow ing the sound to roll around overhead. Scenery, both hanging and standing, was of great benefit in its absorption qualities. COMPENSATE FOR NO LOFT Many newer houses without lofts have also had trouble with acoustics. In most cases an Ozite blanket has overcome this reverberation: but in some instances a frame built against the rear wall, covered with an exposed rock wool blanket, covered with a netting of chicken wire has been A CONFUSION OF TONE One of the greatest faults in the older houses was occasioned by the dome, as somewhere in the auditorium (generally in the choice seating) one would notice a terrific confusion of tone. There is no practical answer to this problem for the dead space deflects the sound completely away, and to cover the entire dome with a highly absorbent material would be very expensive. A further cause of trouble in old houses was the untreated balcony fascia which 'Mr. Boiler is a member of the architecturol firm of Robert Boiler and Dietz Lusk jr. 12 An untreated balcony fascia often caused confusion directly be/ow the fascia in older theatres. Sometimes this was overcome by using ornamental carvings or with an irregular shape to break up the sound However, OS in most modern houses, a better solution is to design the fascia straight and treat it with acoustical material as was done in the Roxy Theatre, Springfield, III, shown above. The MODERN THEATRE SECTION

— necessary to overcome this difficulty. Often a slight diversion of the speakers can cause considerable confusion. I can recall one instance on an opening night one of those openings where they roll the carpet down the aisle as the audience walks in—the sound had been installed but not checked. A strike was called by the sound men, and it lasted for three months. The acoustics were terrible, and it looked as if a small fortune would have to be spent to correct the condition if all walls and ceiling would have to be covered with acoustical materials to overcome the defect. The strike was finally settled and within 24 hours, the speakers were adjusted, no treatment was necessary, and the house is one of the choices today for major screenings of pictures. AVOID OVERTREATMENT An auditorium can be overtreated to such an extent that all resonance is lost—dead like a violin covered with felt. It will givr out sound but it has no resonance. Many exhibitors have insisted on treating the side walls with a highly absorptive acoustical material. In most cases, this is unnecessary unless it is an extremely high wall or there are some disturbing conditions such as extreme wall projections or offsets. However, it is advisable to avoid smooth plaster on the walls. A fine sand or light dash finish plaster is always more satisfactory. The ceiling can always be treated, sometimes to no great advantage, but never detrimentally. The rear wall, especially when of great height, should be treated with the best type of acoustical tile or absorbing materials. The rear wall should not be curved. This has been the source of considerable confusion. It has been overcome in some instances by setting the acoustical material in a zig-zag fashion. DIFFERENT VALUES IN MATERIALS Acoustical materials have different values, perforated acoustical tiles generally have the highest value; soft cane-like tiles such as Celotex being next in value: with acoustical plaster generally of least value, having about 50 per cent the value of cane fiber tiles or 30 per cent the value of perforated acoustical tiles. This isn't intended to condemn acoustical plaster, as my preference in all cases leans to a recognized manufacture of acoustical plaster on the ceiling or where large areas can be covered; but we still prefer perforated acoustical tiles on the rear wall, or in any area where considerable absorption is recommended. A very satisfactory acoustical material which has been on the market for several years is asbeston limpet as it has very high absorbing qualities, equal to perforated acoustical tile. It is an asbestos fiber material, sprayed on, in generally a threequarter-inch thickness and has the appearance of a coarse texture plaster. It is very soft and should be kept out of hand reach. Ornamental pressed or molded felt panels Fabrics and draperies have always beert of great value in achieving good acoustics in the theatre. In the Langley Theatre, Langley Park, Md., the walls are covered with tapestry, a gold-figured fabric on a green background. The dado is dark green leatherette. The 121 feet of gold-colored, hammered satin draperies not only add to the luxurious effect but are of value acoustically. of a deep pattern mounted on furring strips are highly satisfactory and equal to the best of acoustical tiles. Many of the broadcasting stations prefer this treatment. Fabrics have always been of great value. Sometimes they are backed with felt, or even flannel, and when hung loose have a value equal to the best of acoustical materials. In many cases, draperies hung at The dome ceiling frequently used in older theatres has definite disadvantage to good acoustics. A great confusion of tone occurred somewhere in the auditorium, and usually in the choice seating. The dome is to be avoided as there is no practical way to solve this problem except by covering it entirely with a highly absorbent material. the proper location have overcome trouble in that area. The fully upholstered opera chair and carpeting over heavy padding have been two of the greatest benefits in acoustical correction. The difference has often been very noticeable when new upholstered chairs have been installed, replacing veneer back chairs. BOXOFFICE January 3, 1953 13