Journal of the Society of Motion Picture Engineers (1930-1949)

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ABSTRACTS Selenophone: A Variable Area Sound Film Device. P. HATSCHEK. Kinotechnik, 11, Aug. 20, 1929, pp. 436-8. A description of the general principles of the Selenophone sound film system. The torsion galvanometer employed consists of a transverse vibrating metal band in a strong magnetic field. The motion of an illuminated slit attached to the vibrating band is optically magnified 100 times and recorded on the film. For reproduction the "condenser" type of selenium cell is used. The change of resistance of selenium cells upon illumination is known to be accompanied by considerable lag, the greatest lag occurring when the light is decreased. This undesirable property of the selenium cell can be compensated largely by the use of an amplifier vacuum tube operated during the lag period. With the rapid light fluctuations and such an arrangement, the fatigue of the selenium cell is also minimized. The exact details of the compensation method employed in the Selenophone have not been made public. Talkies Have a Past! J. F. RIDER. Mot. Pict. News, 39, Mar. 2, 1929, p. 627. A brief description of the outstanding discoveries which made sound motion pictures possible. In 1857, M. Leon Scott made the first record of sound vibrations. Sound was first recorded and reproduced by Edison in 1877 in a tinfoil record; the process was improved by Bell and Tainter in 1887 who used wax records. In 1889 Bmil Berliner patented the disk record which, with improvements, is now in use. The change in resistance of selenium with change of light intensity was first observed in the 19th century by May, the operator of the Ireland terminal of the transatlantic cable. Interest in the sensitivity of selenium and an effort to overcome the lag in its response caused much investigation which ultimately produced the photo-electric cell. This cell was improved by deForest in 1907 who produced the vacuum amplifying tube. Running the Talkies. XXII. Naturetone. R. H. CRICKS. Kinemat. Weekly, 150, Aug. 15, 1929, p. 69. Comments on the Naturetone equipment for the reproduction of disk-recorded sound. Separate turntables must be used for low speed and high speed records. The speed control is described and stated to be satisfactory. The sound is to be recorded on cylinders in place of the usual disks. Sound-proof Studios. Kinemat. Weekly, 150, Aug. 22, 1929, p. 54. The construction of the new sound-proof studio of the British Talking Pictures is described. To exclude exterior noises and prevent internal reverberation, air-spaced concrete walls are used, with an inner shell of sound absorbing material. The floor is laid on thick felt runners, with a layer of plastic material [bitumen — Abstr.] adhering to the underside of the boards. There is a tank 33 by 32 ft. sunk in the studio floor, arranged for underwater shots. The studio is 120 by 93 ft. in size, stated to be the largest of its kind in Europe. Production lighting is incandescent. [The wiring of the lighting system is arranged in a false ceiling, and all leads and lamps will be dropped from galleries above the studio so leaving the floor clear. — Abstr.] Acoustical Control of Theater Design. H. I,. COOKE. /. Frank. Inst., 208, 259