Exhibitors Herald World (Oct-Dec 1930)

December 27, 1930 EXHIBITORS HERALD-WORLD 31 currents and set the ribbons to their proper spacing without introducing expensive delay circuits as auxiliary equipment. Therefore, in setting up the device, the spacing of the ribbons is reduced to something considerably less than their normal spacing but not as far as complete closure. Furthermore, the latitude of the photographic emulsion is not infinite and also limits the extent to which the closure of '.he ribbons may be effected without exceeding the straight line part of the emulsion characteristics. Since this new method contemplates recording over the part of the film characteristic, and within the limits of this characteristic previously utilized, there is no change in film technique. The processing which produced the best quality of reproduction with the former method gives 'he best quality with this new method. Referring to Fig. 1, which is an approximate characteristic of the ground noise obtained from film of various densities, the point A indicates the approximate density employed in normal recording. By shifting the ribbons to have something less than their normal spacing, we can increase the density during the quiet portions of the sound track to point B. This results, then, in a reduction of the noise in the quiet intervals. Then, as the sound currents are applied to the valve, its spacing automatically varies, so that it at all times has sufficient carrying capacity, as represented by the spacing between the ribbons, to carry the applied sound circuits. A slight amount of margin is always established as a factor of safety, in order that a sound which builds up suddenly will not clash the ribbons. The manner in which the carrying capacity of the light valve or, in other words, the spacing of the ribbons varies with the applied sound currents is illustrated in Fig. 2. It will be seen from this that for weak sound currents below a certain minimum amplitude the ribbon spacing is always the minimum, and the average spacing is unvarying. As the sound currents build up to near their maximum amplitude, it is seen that the average spacing of the ribbons (or their carrying capacity) is gradually increased up to a maximum which corresponds to thatof the normal light valve. As the input is further increased, there is no further increase in the ribbon spacing, and clash occurs as in the normal light-valve. It is entirely possible to continue the carrying capacity of the ribbons upward by allowing their spacing to exceed the normal spacing. No useful purpose is served by this, however, since the carrying capacity of the photographic emulsion 4 ( T^ HE Little Theatre with the College Edu cation," situated in heart of the University of ■*■ Southern California district, Los Angeles, might well be termed the "little theatre with talk ing picture education." For it was not long ago that the house, using De Forest Hollywood Junior equipment, was presented with a mark of honor, the HERALD-WORLD bronze plaque "for thr high quality of its reproduction of sound pictures." Dr. Lee De Forest, inventor of the De Fores t Phonofilm, personally presented the plaque in Paul H. Heiser and Walter Joslyn, owners and operators of the University theatre. De Foresi also personally 'supervised the installation. "There is no question but what the house is onr of the most outstanding examples of correct sound reproduction in Los Angeles," De Forest said upon congratulating the University owners on the marked effectiveness of the projection, sound and policy. The presentation ceremony took place immediately following the first matinee showing and was concluded with the taking of photographs in the lobby, after which the plaque was hung in a prominent position in the foyer. would be exceeded by so doing and an effect equivalent to clashing of the lightvalve would be obtained. Therefore, the device has been purposely aranged so that photographic overload and light-valve overload occur simultaneously, if the recording lamp has been set for normal recording. The general principles of noise reduction for sound records on film may be applied to other than the present form of lightvalve recorders by making circuit changes as required by the particular type of equipments involved. Operation of the apparatus employed in this recording system is relatively simple, although considerable time and effort have been spent in its development. The equip ment is divided into two units — an amplifier located usually at the location ol the main amplifiers and a control unit fed by the amplifier and located at the film recorder. These units are shown in Fig. 3 and Fig. 4. Adjustment of these units is simple and means are provided for checking the adjustments quickly and at fairly frequent intervals. At the present time commercial record ings are being made with a reduction of ten decibels in the ground noise. It is ex pected that as more experience is gained in the use of this equipment, the noise re duction may be increased. Even ten deci bels is a very noticeable reduction and permits an extension of the volume range to a point where sounds previously completely obscured in ground noise become definite!) a part of the reproduction with a conse quent considerable enhancing of the dra matic effect and naturalness. The practical elimination of this ground noise in the the atre gives to the audience a feeling of be ing present at the action and a removal of the mechanical from the sound. The aver age theatre goer's reaction seems to b< one of finding the picture "easy to listeri to" and possessing a naturalness which al but places it in the class of "original" in stead of "reproduction." Copyright, 1930, by Academy of Motion Picture Arli and Sciences Printed in U. S. A. Twentieth Paper in Technico. Digest. FIGURE 4 Noise Reduction Control Unit Show "Noiseless Sound" Western Electric's new process for the elimination of foreign noises in film production was recently demonstrated in the private theatre of the Famous Players' ex change in Montreal. Exhibitors and engineers composed thr majority of the attendance. The program was sponsored by the Northern Electric Company.