Motion Picture Herald (Mar-Apr 1941)

pHHM p p "1 PROJECTION SOUND REPRODUCTION THE SCREEN Academy Acoustic Recommendations C] Examining the latest standards of the Research Council for better sound By GEORGE SCHUTZ WITH PUBLICATION in the March issue of the Society of Motion Picture Engineers Journal, the acoustical recommendations of the Research Council may be taken as official, and they now become available for general promulgation and comment. Developed by the Standardization Committee of the Research Council which is the technical division of Hollywood's Academy of Motion Picture Arts & Sciences, these recommendations represent further effort of Production to bring about a greater competence among theatres to complete the job begun in the studios. The Council established a group of technicians for study of theatre practices several years ago, and standards on a number of aspects of sound reproduction have resulted. In view of the haphazard practices that have generally characterized handling of the acoustic factors in theatre design, the acoustical recommendations must be praised as another expression of the Council's practical, serious interest in what happens to film product after the creative community gets done with it. Noting the year of these recommendations, and recalling that of the establishment of sound, one may remark, perhaps profanely but also quite plausibly, that this is a hell of a time for the industry to take some official, constructive notice of acoustics as part of the sound transmission system. The delay cannot be blamed, however, on the Research Council, which, at least in its present structure and purpose, is of quite recent origin. Then, too, it has been the habit of the business to shy away from all operations and processes of the business not immediately concerned with "showmanship," which has been (and still is in many quarters) thought to be exclusively a matter of shouting as loudly as possible about a picture — a natural hangover from the film's carnival-like beginnings. Being an integral part of the business, the Research Council, in both its efforts to standardize studio practices and its comparable interest in the theatre, gives rather official recognition of the fundamental differences between the Motion Picture and the other kinds of showbusiness. The acoustical recommendations cover much the same ground as the material on acoustics that has been published in Better Theatres, particularly during the last three or four years, and notably in the special articles and regular column of C. C. Potwin. In presenting the standards recommended by the Council, it is therefore proper to consider wherein they run counter to practices that have been either recommended or presented as permissible in these pages. The Defects of Rules At the outset, of course, the theatre operator and designer may properly bear in mind that it is difficult to lay down a set of rules that will cover every variation in conditions encountered among all theatres. There are things that one should do, things that one must not do; but these still leave a lot of things that one can do without being guilty of giving only casual, rule-ofthumb consideration to the acoustical side of sound reproduction. First of all, the acoustical design and treatment should not be treated in such general terms that the theatre operator or his architect is left more or less in the dark as to how to proceed with an actual design problem. Since each theatre involves a different design, in view of essential variations in the contour and the dimensions of the plot, the arrangement of seating, variations of floor pitch, etc., it is axiomatic that the fundamental requirements for acoustical planning will change with each theatre. Ideally, the theatre structure would be developed around the acoustical and other engineering requiremnts, but in many cases there are other limiting factors which make it necessary that a suitable compromise be accepted. At the same time, the architect must be given some freedom in design. While acoustical shaping undoubtedly does have architectural value, the designer usually requires more guidance than a general recommendation will give him if he is to develop a structure that will ultimately satisfy the demands of both sound and appearance. Cubage and Proportions For example, the committee's recommendations begin : "The cubical contents should be kept to a minimum consistent with the number of seats required. . . ." We might justifiably ask, "What is the minimum in relation to seating?" and, "What is the maximum limitation?" Data covering this point have been published, but do not appear in the Journal's presentation of the recommendations. Again : "The auditorium width should be from 50% to 70% of the length and the ceiling height should not be more than 40% of the length." Now in acoustical design today, the concept of average ceiling height is losing its significance. There is a good deal of variation in ceiling height with variations in floor pitch, independent of architectural considerations, and rather than to give a percentage of auditorium length that should be used as a standard for ceiling height, which can lead to misunderstandings, it would seem to be more practical to let the ceiling height be determined by the desirable cubic volume (as well as by the projection and other acoustic requirements) after the floor plan proportions have been established. As shown diagrammatically in the June 1940, issue of Better Theatres, the length of the floor plan of the auditorium proper should not be less than 1.4 times the width, nor greater than twice the width. In determining ceiling height, it should be borne in mind that it is possible to bring the ceiling down to a point too close to the audience, so that objectionable reflections may be encountered even though the ceiling is splayed or tilted. In other words, sufficient height should be assured BETTER THEATRES: March 8, 1941 47