Theatre Catalog (1946-47)

o¥ Clear, Distinct Sound Should Be Standard Brief Consideration of Possible Defects In Sound-Reproducing Equipment and Film As stated in another article, the motion picture is Loew’s merchandise and must be perfectly presented. This article dealt with visual projection. It now follows that oral reproduction is so closely aligned and associated with the projected picture that it cannot possibly be separated from it. As in the proper visual presentation of a motion picture, the first consideration in reproducing the sound in the theatres should, of course, be the comfort of our patrons. Comfortable sound reproduction includes three prime factors: Good intelligibility, even distribution of the sound throughout the theatre and a comfortable volume. If there is distortion, intelligibility is destroyed. If there is insufficient or too much volume, it tends to destroy the comfort of the patrons and constitutes poor reproduction. Improper distribution has the same effect. The physical nature of sound reproduction equipment, however, is entirely too complex to discuss in great detail here. When it is realized that we reproduce recorded sound which is thousands of times below the threshold of hearing, and multiply this many times through a highly complicated system of wiring, condensers, filters, and vacuum tubes, it will be readily apreciated that the actual process of keeping this equipment in first class operating condition becomes a matter for thoroughly-trained technicians and competent projectionists. The purpose of this article then is to point out briefly and simply the results of some of the defects which may occur in the sound reproducing equipment, or the film. NOISE AND DISTORTION Some of the commonest causes of noise and distortion in sound reproduction are occasioned by various film conditions or projector sound equipment misalignments. For instance, one type of sound distortion is created by blemishes in the sound track emulsion, such as pin holes, scratches, foreign particles and emulsion cracks. As previously stated, this condition can only be corrected by acquiring a good print. Several of the misalignment effects, which are heard in sound, can best be described as a “wow,” which creates the effect of a waving, tonal wail of a siren, and is normally caused by lack of pressure on the film passing through the sound head. Calling the projectionist’s attention to this distortion will serve to rectify this condition. Another unusual sound distortion emanating from the horns is technically ealled “flutter,” which can best be deeribed as a rapid, wobbling effect. Flutter tends to prolong the reproduced sound and is particularly noticeable on individual piano notes as well as on all 320 LL Lester M. Isaac, M. D. O'BRIEN, and F. W. BorrrcHER Projection Department, Loew's, Inc. other musical instruments. Some of the causes of this effect are tight guide roller, tight light gate tension, excessive film loop, hooked sprockets causing back lash in film movement, jerky film take-up adjustment, or a sticking film pad roller or idler. Another more mechanical type of “flutter” sound is caused by an aged exciter lamp which has outlived its usefulness. CRACKLING Perhaps the most common distortion occurring in sound reproductions is a crackling sound, which can be likened to crunching paper effect and can be introduced by several abnormal mechanical conditions. For instance, loose elements in photo cells or vacuum tubes, poor or corroded socket connections, loose wiring or terminal connections. In the same category would be the normal deterioration of resistors, condensers, contacts or open circuits in volume controls or changeover switches—these, of course, would be subject to more thorough investigation and repairing than the projectionists are normally equipped to handle. If the every effort made by the projectionist and the service engineer to locate the source of the crackling distortion noise meets with no success, one may look for and expect cracked diahpragms in one or more of the high or low frequency loudspeaker units in the horn system behind the screen. EXTRANEOUS NOISE A seasonal noise which can appear as distortion in the reproduced sound may be occasioned by vibrations, transmitted by machinery, generating a mechanical vibration which may be misunderstood as emanating from the horn system. For example, starting up the theatre ~airconditioning system or fans can generate a sound which was not apparent prior to the starting of this machinery. When such a complaint appears, it is suggested that the management immediately notify the projection department. Similar mechanical noises sometimes also may be traced to equipment not associated with sound reproduction such as vibrating light fixtures, loose equipment stored near the horn system, and even The accompanying consideration of good sound is reprinted by permission from the June 1, 1946, issue of Lo!, house organ of Loew’s Inc. loose chairs or parts of chairs and other loose miscellaneous equipment in or about the theatre. Certain theatres are located in close proximity to transit systems such as subways, elevated, or street car lines, or in the immediate vicinity of local construction projects so that rumbling sounds, created by these conditions, will be immediately recognizable by the management as originating outside of the theatre and not attributable to defects in the sound reproducing equipment. A sudden change of sound volume in your theatre may be occasioned by one of several things, including any defect or maladjustment of the exciter lamp, or its associated circuits, which will immediately tend to change the volume of the running projector. Also in this category are improper exciter lamp adjustment; a change in exciter lamp intensity due to aging of the lamp; exciter lamp-power supply varying due to incoming power service variations, or defective tungar or rectification equipment. An exciter lamp which has been in use beyond its rated useful life tends to blacken from carbon deposits, coating the inside of the glass and reducing the intensity of illumination. It is recomended that such lamps should be replaced in an early stage of such a blackened condition. CHANGES IN SOUND VOLUME Lubricating oil seepage into any portion of the sound reproducer optical system such as the lens assembly, the sound lens slit, or prism assembly, will serve to impair the efficiency of the entire sound optical system and, thus, reduce volume at the horns. Such conditions can be rectified by the sound service company. In the event of any of the component portions of the sound optical system appearing out of adjustment, also causing changes in sound volume, notification of the sound servicing company will effect an immediate remedy. Photo cells which have outlived their usefulness, or improperly adjusted photo cell voltage, or any factor which contributes to a variation of voltage will also create a change in the sound volume. Among the myriad causes of changes in sound yolume (many of which are beyond the control of the projectionists) might be listed, worn or defective switch contacts; deteriorated wiring and terminal connections on volume control equipment; old or defective vacuum tubes; and failure of the more intricate component parts of the amplifiers such as filters, condensers, resistors, transformers and associated controls. Perhap the most common defect of sound volume changes, however, is 0¢casioned by variations or a drop in the source of incoming electric service, oF excessive loads on the building service. This will naturally affect the voltage sup THEATRE CATALOG 1946-47