Kinematograph Year Book 1942 (1942)

294 The Kinematograph Year Book. head. By requiring only that all prints not recorded for control track reproduction have a clear sprocket-hole area, complete interchangeability of prints is obtainable. It is pointed out that any modern reproducer system can be modified to provide multiple-speaker reproduction, and the improvement obtained is a real one. Western Electric. — A detailed description of the system of stereophonic recording and reproduction developed by the Bell laboratories and Western Electric, appeared in the October issue of the S.M.P.E. Journal. The general requirements are first discussed for the ideal recordingreproducing system, as determined by the characteristics of hearing of a typical group of auditors in a theatre. Quantitive values are set down as ideal objectives. Although the components of the transmission assembly — loud speakers, amplifiers, etc., were available to meet the requirements, no recording medium was known which woidd record the wide dynamic range of intensity levels, which the objectives indicated as being necessary. The system was briefly described in a recent B.K.S. Bulletin, which explained that the wide-intensity range was met by using a " compandor " (compressor-expander) in the electrical system. Reasons were given for the selection of the particular " compandor " used, for the employment of variable area rather than variable density, and for using three instead of a greater or lesser number of channels. A description is also given of the " enhancement " feature which makes it possible to re-record for the original recording, at the same time realising any desirable changes in the dynamic range or frequency response in each of the three channels. The electrical system is described, including methods of noise reduction, maximum suppression of noise and freedom from distortion, volume control in relation to pre-recording and reproduction ; film propelling mechanism (the machines are designed to handle film in 2,000-ft. lengths), the light valve ; equalisation of resonance-region response. The mechanical design with several interesting features, among which are mechanical robustness, protection against dirt and moisture, built-in ribbon and optical adjustments, and an optical system integral with the vslve structure. RCA. — Meanwhile RCA have adapted the lessons learned in the design of " Fantasound " to the perfection of a simpler reproducing system, which, while possessing the improved sound characteristics of the original, will be within the reach of all. This is considered to have been achieved by the RCA Panoramic Sound System, for which only a single film will be required and entails very little adaption of the existing reproducing system, the main difference being the recording track. Extra sound recording and printing costs will be negligible. Some months ago an RCA Panoramic Sound System was made available to Hollywood film producers, and the Academy of Motion Picture Arts and Sciences, so that they might study it with the view of arriving at uniform film standards for all productions. Since the characteristics of the reproducer system must dovetail with these recording standards, no general sale of RCA Panoramic Sound Systems will be made until such standards are set. In the meantime, a limited number of experimental installations, under way or contemplated, in key Hollywood and New York theatres, will provide further valuable data. Vitasound. — Details of the Warner process " Vitasound " indicate a similarity to the simpler form of the RCA system. This also requires but a single picture-and-sound film, and the less involved mechanism needed provides a practical alternative to the more elaborate equipment which, although less perfect theoretically, is capable of superficially similar illusions. Three sets of speakers are needed, but they are fed through two amplifier channels and no auditorium speakers are used. Existing sound-heads and the amplifier channels need modification, the latter for variable-area operation ; a control panel for handling the variable-gain control currents would have to be installed. Volume expansion is secured by means of a control track, which is actually recorded in the perforation margin of the film.