Motion Picture Herald (Jan-Feb 1939)

(p\annlnc\ if 'fwzntihinq . . . a department of news and guidance on design • decoration construction methods m carpeting • furniture m Co-Ordinating Acoustics and Architecture in the Design of The Motion Picture Theatre By C. C. POTWIN and BEN SCHLANGER • A condensation by the authors of a paper which they presented before the Fall 1938 Convention of the Society of Motion Picture Engineers, and which is now made available with its publication in the February issue of the Society's Journal. A critical distinction of modern architecture from prior technique lies in a more candid evaluation of function. To be really modern or functional in architecture is to go straight to the purpose of a building, and to develop it in plan ajid structure according to an honest acceptance of that pkvpose, providing in the forms and devices khat serve it a beauty that is inherent. When the ideal of functional efficiency and proper aesthetic quality becomes our guide in designing a motion picture theatre, the precepts of sound, light and vision supply the basis for fundamental planning. Correct vision, without obstruction, has been provided in a number of new designs. Lighting in the auditorium is now being given more study. Air-conditioning, proper seating, and general arrangement and appointments, are also receiving much more consideration ; however, practically no attention has been given in previous design to the relationship that exists between acoustics and the fundamental plan of the theatre. This does not mean that the acoustical problem has received no attention. It has often received thoughtful treatment, but more specifically from what might be termed a corrective rather than a constructive point of view. The corrective approach has become common practice because ( 1 ) the preliminary basic form of auditoriums has not been planned for best acoustics; (2) the total cubic volume of the auditorium structure has not been held down so as to fall within desirable limits, as it might have been in many new designs; and (3) the past tendency to follow tradition in architectural design practice has usually made it mandatory to utilize corrective methods. There is one other reason that should not be overlooked. At the time speech and music were added to film's, sound absorbing devices were required for many existing structures having poor acoustical conditions. Perhaps from force of habit, reliance upon these devices has extended into the planning of new theatres. As a result, basic acoustical design has been overlooked as one of the sources of effective architecture. Acoustical materials for the treatment of motion picture theatres are in no wise to be regarded as unnecessary ; such materials are commonly required for new theatres having very large seating capacities, for existing theatres having fixed forms which produce objectionable sound reflections, and for both new and existing structures which have excessive cubic-foot volumes per seat. It is proposed in this paper to show that more efficient and more economical theatre structures can be built when basic acoustical requirements are co-ordinated with the other primary functions of theatre planning. Acoustical Requirements Two fundamental factors which must be considered as the first step in the functional acoustic planning of a motion picture theatre are: (1) the preliminary outline of the auditorium, establishing its proportions of length, width and height; and (2) the volume, or cubical content, of the auditorium structure relative to the seating. Ratios of Width to Length The most efficient control of sound reflections and the best distribution of sound energy can usually be obtained in theatre auditoriums where the ratios of width to length fall within the limits of 1 :1.4 and 1 :2. When the length becomes greater than twice the width, difficulties arise from a multiplicity of sound reflections occurring between the side walls. When the ratio of width to length is less than 1:1.4, the resulting design becomes an unfavorable one from the standpoints of proper sound distribution and vision. This design also creates an unusually large rear wall, which is often a source of objectionable sound reflections. Height of the Auditorium Ceiling The limits of ratios recommended above for the floor plan are not meant to suggest that a strictly rectangular outline must be adopted. These ratios also apply to the 20 Better Theatres