Patent GB-401697-A (GB)
Title: Process for the recording of sound
IPC: G11B7/00
Filed: 1932-02-15
Abstract: 401,697. Recording and reproducing sound. SCHAPOVALOFF, S., 23, Langasstrasse, Berne, Switzerland. Feb. 15, 1932, No. 4436. Convention date, Feb. 13, 1931. [Class 40 (ii).] A process for recording sound on films consists in simultaneously recording without distortion on one record to a relatively small scale and on another record to a relatively large scale, the record of small scale being made more intensively (i.e. of greater density) than the other record in a proportion corresponding to the ratio of the scales in order to compensate for the difference in scale. In the case of variable area records, the record of small scale is uniformly darker in the negative than the other record, and in the case of variable density records, corresponding points of the two records will be darker in the negative of small scale than in the other record. One of the records may be of the variable area type, and the other record may be of the variable density type. In the production of variable area records, two light sources e, e<1>, Fig. 5, each associated with a galvanometer g, g<1>, are adapted to record on a separate zone of a film strip. In order to produce the small scale record, the action of the galvanometer g<1> is weakened by a potentiometer i so that its deflections are reduced in the desired proportion. The density of the large scale record may be reduced correspondingly relative to the small scale record either by placing a filter f between the light source e and the galvanometer or by the use of a light source e<1> of greater intensity for recording the record of small scale. Diaphragms k, k<1> are inserted between each galvanometer and the corresponding record zone, and these may be set so that the sounds are completely recorded in both zones or so that each zone only records sounds within certain limits of amplitude. Thus in the zone of small scale there may be recorded only sounds above an arbitrary amplitude, and in the other zone, sounds above this amplitude are recorded. The amplitude ranges of the two record zones may overlap, if desired. The two records may be recorded within or outside the usual perforations of the film strip and either directly next to each other, superimposed, or in spaced relation. The records may be on opposite faces of the film. The Specification as open to inspection under Sect. 91 describes also (1) the recording in one zone of sounds above a certain amplitude, and in another zone, sounds below this amplitude to a larger scale, without compensating for difference in scale in the records themselves. Such records are reproduced simultaneously by separate light beams, each cooperating with a photo-electric cell, amplifiers and loudspeakers. The amplifier and loudspeakers associated with the small scale record are of larger output than those associated with the other record. Alternatively, reproduction may be effected by using two light sources of different intensity for the two records, or two different photoelectric cells ; (2) the recording of the sounds to different scales in more than two parallel tracks, and it is stated that the records may be black or coloured ; (3) a method of recording the two records in superimposed zones by employing a single galvanometer g as shown in Fig. 12 (Cancelled). A reflecting diaphragm l is so positioned that the deflections of the mirror h produced by low amplitude sounds cannot reach the film, but are reflected on to a mirror m and thence on to the film. Sounds of larger amplitude pass the diaphragm l and are recorded at reduced scale on the film ; it is stated that the difference in scale is produced by adjustment of the mirrors h, l, m; and (4) the copying of the sound records by contact or projection printing with the films immersed in a liquid, such as benzol. This subjectmatter does not appear in the Specification as accepted.