British Kinematography (1948)

163 an angle and are therefore more suited to studio monitoring applications where acoustic conditions are good. Future Developments Prior to the war there were several special developments in sound reproducing equipment. Push-pull sound tracks were introduced, but so far have only found general acceptance in this country in studios for original recordings. Stereophonic systems have received considerable attention in the U.S.A. The Disney feature production " Fantasia " was accompanied by the development of a multi-track sound reproducing system including the use of a control track by means of which the volume range was extended 30-40 db. and controlled automatically during the showing of the film. Further work on the use of relatively simple control tracks for the same purpose is in progress, and it seems possible that equipment having a greater volume range than the present 45-50 db. could be made available to the industry without much difficulty. The greatest single limitation to better reproduction which we still face in many of our existing kinemas is unfavourable acoustic conditions, and there is immense scope for the application of corrective measures, in order to do full justice to the high standard of which a modern system is capable. REFERENCES 1. Research Council of the Academy of Motion Picture Arts & Sciences. May 17th, 1940. 2. E. G. Shower and R. Biddulph. Journal of Acoustical Society of America. Oct., 1931. 3. T. E. Shea, W. A. MacNair, V. Surbrize. Journal S.M.P.E. Nov., 1935. 4. W. J. Albersheim and D. Mackenzie. Journal S.M.P.E. Nov., 1941. 5. D. Foster. Journal S.M.P.E. Nov., 1939. 6. Projection Practice Committee Report. Journal S.M.P.E. July, 1937. 7. E. D. Cook. Journal S.M.P.E. Oct., 1935. 8. Academy of Motion Picture Arts & Sciences — Sub-committee Report. Journal S.M.P.E. Feb., 1947. 9. L. Audigier and Others, /. Brit. Kine Soc. Mar./Apr., 1947. 10. Olson and Preston. Journal S.M.P.E. Oct., 1946. 11. Beers and Belar. Journal S.M.P.E. Apr., 1943. 12. Lansing. Journal S.M.P.E. Sept., 1944. DISCUSSION Mr. R. H. Hollyman : Has Mr. Sinclair Mr. R. H. Hollyman : Does not the any personal preference for the system of question of light scatter arise more with the scanning — direct or indirect ? projected slit system ? Mr. Sinclair : I have no personal Mr. Sinclair : Light scatter is un preference. I believe on technical grounds doubtedly a problem, but you must re either system can be equally effective. member in the projected track system, not Mr. R. H. Hollyman : I have had a only is the image of the sound track great deal of experience on different equip enlarged, but also the slit is proportionately ments, and in general I prefer the projected larger, image system. A Visitor : Is it possible to modify the Mr. R. H. Cricks : We hear manufac L.F. speaker housing in such a manner as to turers claiming .0005 in. slits, or even less, increase the L.F. efficiency? on an emulsion .001 in. thick. Is it not Mr. O'Dell : The important thing to better optically to project the track and realise is that to increase the efficiency of then scan#it, rather than to try to produce the L.F. acoustic output, you must try to such a narrow image? utilise the back wave as well as the front Mr. Sinclair : Given equal design, and wave. Since these signals are alternating, given equal quality of manufacture in the it is obvious that you must superpose them optical parts, I do not think there is much so that they emerge in phase. It is for that to choose between the two systems. It is reason that there is a limit to what you can possible that the projected system has some do by that method, not only in improving advantage, but it would be mainly in ease efficiency, but there is a limit to the of adjustment rather than in the actual range of frequencies over which the idea is results obtained. effective.