Projection engineering (Jan-Dec 1931)

Page 22 PROJECTION ENGINEERING Sound projection practice Part (Continued from September issue of Projection Engineering) ITEMS FOR FURTHER INVESTIGATION Preferred Sound Track Size and Location The considerations which dictate the preferred sound track size and location are twofold — first, engineering, and, second, economic. For the present the second of these dominates. Engineering considerations tend to favor an increase in sound track width over the present track, although such an increase cannot be carried on indefinitely without encountering further engineering difficulties. A number of locations for the sound track differing from the present have been proposed. The majority of these offer little to be gained from an engineering standpoint. Their effect is mainly to permit a change in the present picture size, and the principal difficulty standing in the way is an economic one. Until it has been possible to make a further engineering study of this problem, it would appear to be undesirable to disturb the producers' and theatre owners' efforts to stabilize their economic positions by the introduction of equipment necessary to effect a relatively slight engineering or artistic improvement. Sound from Separate Film At the time when sound recording and reproducing was just getting a start, the need for double film was felt rather strongly. Some difficulty was experienced in the proper processing of both sound and picture on the same film, and, in addition, the theatre reproduction apparatus was less effective than it is today. At that time the industry was often able to obtain better than normal results by using the double film. At present the situation is quite different. Theatre reproduction apparatus has been greatly improved, and, moreover, a large part of the available theatres have been provided with sound apparatus at considerable cost. To supersede this apparatus or to modify it in any way would represent a substantial increase in cost to the theatre and would present an economic problem which should not even be proposed unless substantial advantages are to be derived from the change. Separate sound film installations would permit : ( 1 ) control of sound film independent of the picture ; (2) separate handling of the release print in processing; (3) wider sound track; (4) higher running speed for sound track. There are no data existing to show that these improvements warrant an expensive change. In the first place, it is no longer considered a serious handicap to the sound record that in variable density records a negative development must be accommodated to the processing of the composite print. By proper choice of conditions, satisfactory results can be obtained differing only in volume from what might be obtained with the separate sound film. Noise reduction technic applied to the composite sound record is adequate for practical theatre requirements. Secondly, studio and laboratory technic has found practical solutions of most of the problems of development of picture and sound records on the same film, in positive form. This did not always seem feasible, but present results indicate no particular handicap. As a matter of fact, the positive control enforced by sound requirements has produced a general improvement in average picture print quality in many cases. Somewhat the same reasoning applies to the wide sound track. With the track twice as wide as at present, an improvement of the order of three db. in signal-to-noise ratio should be obtained, with no change in quality. This improvement is scarcely sufficient to justify a large change in theatre apparatus, in the light of noise reduction studies which are at present under way. The case of high running speed for the sound track has advantages since the greater the speed of the track the greater the ease of recording high frequencies. There should certainly be no difficulty, however, in recording frequencies up to 6000 or 7000 cycles on existing film stock running at the present standard speed. The present recording and reproducing equipment, at least with modifications and improvements which will be made as the art progresses, should be capable of recording and reproducing this frequency range. H. B. SANTEE Sound Committee, S. M. P. E. It would, therefore, seem wise to exert efforts to obtain good, clear reproduction with present facilities rather than to introduce additional means for extended range at this time. Ultimately the state of the art may warrant the recording and reproduction of very high frequencies in the audible range but it is not believed that the time is opportune to consider costly changes toward this until full advantage is taken of present equipment. An important economic phase of the handling of film is the mechanism of release through the exchanges. Handling and shipping problems are such that the extra cost and complication of handling a separate medium for sound is almost prohibitive. Moreover, the problem of maintaining synchronism must be admitted. No numbering system, however complete, can be as satisfactory in this respect as to have the picture and sound records unalterably tied together on the same film. Even at present, the producers annually furnish thousands of feet of short replacements to take care of inadvertent or deliberate changes of a print in the exchange or theatre to accommodate a particular situation. It has never been possible thus far, to prevent such changes being made. Obviously, it would be very much harder to handle this phase of the problem on a double medium basis. In the light of this brief analysis, it is the Committee's definite recommendation that the Society should take a stand in favor of improvements known to be possible in the present standard composite picture and sound print. {Concluded on page 24)