GB247629A - Improvements in apparatus for recording and reproducing sound - Google Patents

Abstract

247,629. Fournier d'Albe, E. E. Oct. 23, 1924. Optical apparatus.-Relates to apparatus for optically recording and reproducing sound. According to the invention, a photographic record is made by means of light-reflecting reeds attached to resonators tuned to the same frequencies as the reeds. In this way, the sound to be recorded is analysed into constituent vibrations which are recorded simultaneously, by individual pencils of rays, as broken parallel lines on a photographic film. Reproduction is effected by breaking up light from a steady source into intermittent pencils, the frequencies of which correspond with those of the tuned resonators, and passing these pencils of light through the component photographic records on to a selenium cell which operates a telephone in known manner. Fig. 1 shows diagrammatically a recording apparatus in which five resonators b are employed, each carrying a silvered reed b<1>, and each resonator and associated reed being tuned to respond to a particular note. The sound to be recorded is directed from a trumpet a on to the resonators. Light from a source c is reflected from the reeds b<1> in separate pencils, which pass through perforations in a screen g and act upon a moving sensitized film f. The resonators may be rectangular, or as shown in Fig. 4, may be spherical. In this arrangement, the resonator is adjustably mounted in a holder r. Fig. 2 shows apparatus for reproducing from the record f, which is moved between a selenium cell k and a slotted screen i. Intermittent rays or flashes of light, corresponding in number and individual frequency to the notes to which the recording resonators are tuned, pass through a slot j in the screen, and through the separate sound-traces on the record film f to the cell k. The intermittency of the rays is produced by rotating an opaque disc l across a beam of light from a source n, the disc having the required number of concentric rows of perforations m, suitably spaced. Lenses o, p are arranged as shown. Alternatively, the light breaking-up device mav comprise a cylinder having along its length coaxial circles each divided into different numbers of opaque and transparent portions. The record may be interposed between the light source and the breaking-up device.