Fim Recording and Reproduction

In a historical summary of motion-picture sound recording and reproduction, some of the technical problems and solutions are discussed, starting with the conversion of silent motionpicture studios to sound studios. During the early years, both the sound-on-disk system (arner Vitaphone) and the sound-onilm system (Fox Movietone) were used. The film recording method was in its early development stage and the sound quality was relatively poor, but it had many inherent advantages which ultimately led to its universal acceptance. The first commercially successful photographic sound recording system used a variable intensity modulator known as the Aeo-light. This was later replaced by the ERPI light valve which is still in use today. The optical system used with the light valve is shown, and certain photographic requirements for linear recording are discussed. The variable area recording system is the outgrowth of the Duddell oscillograph. The oil damped galvanometer was replaced by a magnetic-type optical modulator, and a more effective optical system was developed. Several sound tracks produced by this unit are shown. Noise reduction methods required by both the variable area and variable density recording systems are described. An unusual type of sibilant distortion caused considerable difficulty in the early variable area sound tracks. The nature of this distortion and the means of correcting it are given. Although magnetic recording is one of the oldest methods known, it came into its own during World War II. Its potential importance to the motion-picture industry was quickly recognized.