SCIENTIFIC SOCIETY.

Press, Volume LXVI, Issue 19917, 2 May 1930, Page 18

SCIENTIFIC SOCIETY.

PRINCIPLES OP THE TALKING FILM. "Scientific Principles of the Talkies" was the subject of an address delivered bv Mr E. W. Hullett at a -wellattended meeting of the Scientific Society last night. 9 During the lecture, which was illustrated by demonstrations qf the action of various parts of the apparatus used in the production of talking films, the speaker explained that the two systems employed were that in which the sound was recorded on a separate disc and that of the sound on the film. "In the sound on disc method," said the speaker, "the sound record i» made exactly as an ordinary gramophone record except that the pick-up arm moves outward from the centre of the record. A motor control box keeps the electric motor driving both light and sound apparatus at a constant speed, which is maintained in reproduction as well as in recording. The film travels ninety feet in a minute, while at the same time the disc makes 38 1-3 revolutions. In this system there is, however, a possibility of faulty synchronisation due to the recording arm slipping a groove, in the rjecord. "With the sound on film method there can be no danger of lack of synchronisation for from separate negatives worked simultaneously the picture and sound photographs are printed together in the making on the one film. By means of a focused beam of light passing through the sound record on the film and falling on a photo-electric cell, electric impulses are set up which, when amplified one hundred, millionfold. are broadcasted from behind the screen as the now well-known sounds and voices of the Talkies. The sound record is printed about fourteen inches lower on tho film than its corresponding picture in order that the portion of film may pass before the "ictnre projector at exactly the same instant that its sound record is in tfte light beam a little lower. At present the general opinion is that better quality sound reproduction can be obtained from the sound on disc method, but as this is liable to get out of synchronisation, the, sound on film method is coming more and more into vogue." At the conclusion of the address the speaker was accorded a vote of thanks.