Projection engineering (Jan-Dec 1931)

SEPTEMBER, 1931 Page 17 noise from the projection room into the theatre, from the ventilating systems, from sources external to the auditorium, and to miscellaneous noise sources within the auditorium. More information is available upon the acoustic power required to provide satisfactory sound volume in an auditorium. It is, therefore, possible to predict more accurately what effect the introduction of absorbing material into an auditorium will have upon the sound volume and, where necessary, upon the electrical requirements of the system. Many improvements have been noted in existing commercial materials and a large number of new materials suitable for studio and theatre use have been developed and introduced in the past year. This has considerably widened the field for obtaining materials having the desired acoustic characteristics for the particular application and which will be more readily acceptable from the standpoints of architectural appearance, fire hazard, and cost. Preservation of Sound Prints The Committee has been fortunate in receiving from a firm prominent in the film industry the results of tests, conducted over a period of two years, of processes which purport to preserve motion picture film. The method used in these tests was to prepare loops of film, half of which were processed and half unprocessed, both sections being taken from the same reel or roll. These loops were projected 300 times, with examination at 100, 200, and 300 runnings, on a specially prepared projection machine, which caused as little wear as possible. The processes tested were such as lacquer, surface hardening, whole surface waxing, chemical impregnation, liquid edge waxing, etc. The noticeable effect of the processes investigated was that the film became seasoned more quickly, so that during the first few times of projection, the emulsion did not collect on the shoes and tracks of the projection machine as is often the case with green emulsion. There was also indication' from this set of tests that liquid edge . waxing provides comparable protection. Once past this initial period, however, it was not evident that the processes provided any material improvement in giving greater lasting qualities to the film. Talking Motion Picture Equipment for Home Use In recent years several talking motion picture equipments have been developed and offered for sale for home use. Practically all of these equipments use a 16 mm. projector with either a flexible shaft or geared connection to a synchronous turntable for disc repro duction of sound. All the devices examined, except one, project 24 pictures per second and employ a turntable driven at ZZl/i r.p.m. This one exception projects 16 pictures per second and the projector and turntable are driven by electrically interlocked motors. In order to maintain synchronism with the 2>2>lA r.p.m. turntable, every third frame is removed in printing from the negative to the positive. At the present time 16 mm. films synchronized with sound are difficult to obtain and are expensive. If an extended library of films were available, it is probable that a larger demand would appear for home talking movies. To GLENN E. MARTIN Progress Committee, S. M. P. E. date, the supply of films is extremely limited and these films are available only in the larger centers, requiring personal application to obtain them and personal return. This mitigates against very extended use of these films and is a serious detriment toward obtaining a large market for the reproducing equip.ment in the home. Talking Motion Picture Equipment for Non-Theatrical Uses Considerable demand is apparent for talking motion picture equipment for non-theatrical uses, this equipment to be used either for advertising purposes, instruction work, in schools, churches, etc. Equipment for this purpose is built by all the leading talking motion picture apparatus manufacturers. The trend seems to be toward a 35mm, film with sound on the film, although some equipment has been built with the idea of using 16 mm. film and a synchronized disc, which permits a picture of sufficient size and brilliance of illumination for small audiences. Libraries are be ing developed which will undoubtedly stimulate the exploitation of such equipment. Sound Equipment in Theatres On January 1, 1931, there were reported to be in the United States 13,515 theatres equipped for sound reproduction and 8,209 theatres unequipped. It might, therefore, appear that during the period of sound equipment installations only about 63 per cent were completed. Many of the theatres now runningsilent, however, are unprofitable houses which may never be able to afford sound equipment. With the decreasing number of silent picture releases, these theatres may be forced to close. It follows, then, that the installation period is well over 63 per cent completed. Perhaps 80 per cent would not be too high a figure. It may be considered that the industry is passing out of the installation period and is now entering a period of stability in operation and of refinement. The novelty value of sound has passed with every indication that sound has become as necessary a factor in the theatre as is the picture on the screen. The first problem of theatre projection is obviously to keep a picture on the screen and to maintain sound from the horns. It so happens that statistics from Electrical Research Products, Inc., are available, which show the ratio of emergency calls to theatre installations in the United States over a period of time. In December, 1928, with roughly a thousand theatres equipped, the ratio of emergency calls per week to theatres in service was about 0.185. In December, 1929, with 3300 theatres equipped, the ratio had fallen to about 0.05. In December, 1930, when nearly 5,000 the '. atres were equipped, the ratio was as low as 0.022. This decrease in emergency calls is caused by improvements in design and manufacture, and to proper and continued maintenance of the equipment. It is logical to believe that the operating troubles experienced with other reputable systems follow somewhat the, same general course. It is consequently obvious that the first requirement of sound projection, namely, consistent and reliable operation, has been achieved. The quality of sound now focuses our attention. Poor theatre acoustics constitutes one of the most serious causes of poor sound reproduction in theatres. Acoustic analyses have been made in a large number of theatres and corrections of the conditions have been made in some cases. It often happens that the theatres less able financially to make the correction need it most. It has been proved in so many cases that improved acoustic conditions result in increased (Continued on page 22)