Patent GB-258864-A (GB)
Title: A method of improving the tone quality in talking films
IPC: G11B7/00
Filed: 1926-09-17
Abstract: 258,864. K³chenmeister, H. Sept. 22, 1925, [Convention date]. Optical apparatus; electric and magnetic apparatus; optical records.-In order to improve the tone of the sound reproduced from a film record the sounds are reproduced at least twice, in such a manner that they reach the ear with a phase difference, corresponding, for example, to a time interval of # to <1>/30 of a second. The object of the invention is to produce an acoustic effect similar to that for which the gramophone construction described in Specification 238,372 is designed. Various methods of carrying the invention into effect are described, involving either the production of special records, or special methods of reproducing from ordinary film records. Fig. 2 shows diagrammatically a method of producing upon a kinematograph film a double sound record such as is shown in Fig. 1. The records 3, 4 are alike, but one is displaced along the film through a distance a relatively to the other. so that there is a difference in phase between the sounds represented by any two parts of the records that lie in the same longitudinal position on the film. Instead of having both records 3, 4 on the same side of the pictures 2, they may be on opposite sides. The method of recording consists in using two optical recording appliances 12, 13, separated by the required distance, the recorders being connected through amplifiers 9, 10 to microphones 7, 8 respectively, these being disposed at equal distances from the source of sound 6. As an alternative only one microphone and amplifier may be used, the two recorders being connected in parallel to the amplifier. A further method of recording consists in arranging the recorders in transverse alignment across the film, and in disposing the microphones at unequal distances from the source of sound, the difference in distance, say 30 metres, introducing the requisite phase difference between the records. Another way of producing a. film having two records thereon of different phase consist in printing from a single negative record two copies upon the same positive film, the negative being slightly shifted longitudinally when making the second copy, Reproduction from such records as those made by the above-described methods may be effected by the apparatus shown in Fig. 8. This comprises two light-sources 83, 84 transmitting light through transversely aligned parts of the records to two photo-electric cells (not shown) which are in circuit with an amplifier 85 connected to one or more loud speakers 86. Instead of combining the effects of the sound-reproducing currents in this manner, separate amplifiers and loud speakers may be employed. Fig. 5 shows an arrangement wherein there is used a film having identical records 31, 32, synchronously produced without displacement along the film. In this case, light-sources 33, 34 separated along the film transmit light through the individual records to photo-electric cells which are connected respectively through amplifiers 36, 37 to loud speakers 38, 39. The phase difference in the sounds reproduced is thus determined by the distance a<3> between the points on the records. through which beams of light pass. Several methods of reproducing from a single sound record in such a manner as to give the desired effect are described. In one method, two sources transmit pencils of light through two longitudinally-spaced parts of the record on to two separate photo-electric cells, each of which is connected to an amplifier which operates a loud speaker. Instead of using two separate lightsources, a single source may be used, the raystrom which are divided by means of reflecting prisms into two separate pencils of light passing through the film at longitudinally-spaced points. The Specification as open to inspection under Sect. 91 (3) (a) comprises also an arrangement in which light from a single source 51, Fig. 7 (Cancelled), after passing through the film 50, is split up by reflecting prisms 52 into two separate pencils which act on two photo-electric cells 55,. 56. These are connected to amplifiers 59, 60 which operate two loud speakers fil, 62, arranged at such different distances from the listeners that the sounds are not heard simultaneously. A similar arrangement of loud speakers may be adopted when these are operated from a single amplifier controlled in the usual way by a single beam of light passing through an ordinary photographic record. The invention is stated to be applicable not only to photographic film records, but also to other sound records "provided on elongated carriers," for example records consisting of variably magnetized steel wires or bands. This subject-matter does not appear in the Specification as accepted.