Projection engineering (Jan 1932-Mar 1933)

MAY, 1932 Page 17 The talking book By Dr. Irving J. Saxl* THE phonograph industry has suffered severe losses in competition with the radio industry. The development of radio improvements has made the present-day radio apparatus more preferable to the average customer than the old-time phonograph. Now the sciences have added new features to the performance of the record reproducing equipment which could not be obtained with the old apparatus. In addition, the added improvements make this new apparatus valuable and independent of the competition of radio. Science which, by bringing radio into the market made serious competition to the phonograph industry, has now, with the very tools of the radio sciences, improved the phonograph so that it is not only useful again but its range of application is greatly widened into a field where there is no competition from radio. Phonograph Difficulties The phonograph was handicapped by two important elements. They were, the minor quality of sound recording and reproduction and the limited length of one sound track that could be recorded upon a single record plate. In addition, the record was heavy and subjected to breakage generally and an editing of the record was impossible. Although today new records have been made available which can play for almost twenty minutes, this type of recording has some disadvantages. The grooves of these vertically cut record plates can be more easily filled with dust than the horizontal Berliner cut, which was considered for a length of time superior to the vertical Edison cut. Therefore they will probably lose their quality of sound reproduction sooner than the horizontal cut. Only practical experience would make it possible to say definitely. The second point seems more important at present. If sound is to be made on these plates then, even if a single mistake is made, the whole plate is worthless, thus creating difficulty in making a record with such plates, and, naturally, adding to the expense of reproduction. *Consulting Physicist. In the present competition with radio, only a machine with excellent sound quality will be able to stand up. Audio amplification, naturally, is the proper means for doing this. In addition, if long records are supposed to be played, proper means have to be found to make possible an editing of the records so that if a mistake occurs somewhere in the middle of the performance, the entire recording procedure does not have to be begun all over again. A proper way of doing this has been found in a new machine, Fig. 1. A narrow strip of film about one-quarter of an inch wide travels from the coil at the right side over a guiding mechanism and is recoiled again by the other coil. In this case an opaque film is used, which is strongly illuminated from two sides, the center of the film by means of the focusing equipment, being centered upon a pholo-sensitive cell. A slip of proper width provides that the right part of the film is reproduced. By this way of projection the reproduction takes place by diffused and reflected light. If transparent film is used, naturally, a light source has to be placed at the opposite side of the film so that the light passes through the transparent film. Six mm. film is used, each side of which carries a separate sound track. The entire apparatus is driven by a small electric motor. The light sensitive device — in this case a selenium cell — is used making possible a greater level of initial amplification and reducing the noise-level. This selenium cell controls amplification equipment of the usual type which works either into headphones or into a loudspeaker. What is the advantage of this type of equipment over the old-fashioned phonograph and what can make it a new and valuable factor in merchandising electronic equipment? Primarily, vacuum tube audio reproduction is well known as giving better quality of sound than mechanical reproduction. Practically a greatly increased length of speech or music can be recorded, say, for about twenty to twenty-five minutes. In addition, in the negative of this speech, those parts in which a mistake has been made can be taken out and corrected so that the recording procedure is simplified and its expense reduced considerably. Editing and cutting of these records is practical. This increased length and quality of sound reproduction makes possible the recording of performances and actions which heretofore have been impossible. For instance, the whole act of an opera, or a whole suite of a concert can be recorded at one time and it is not necessary to turn over record plates and in troduce undesirable pauses. A continuous reproduction can be made also of lengthy works. Should, however, any mistakes be made in the recording of this performance, they can easily be eliminated by simply pasting in, in the desired length, a new record of the piece where the corrections were made. There is at the present time one more important outlet for this type of apparatus which seems to be promising from two different angles. One, that it will provide work for a number of industries and employees, and second, that it will amount to a considerable saving for the state. At present the law in different states provides from $125.00 to $300.00 for each blind pupil per year, for this amount the pupil is supposed to have somebody who will read scientific works to him, or works which will increase his further study and earning capacity. This service of a reader is provided for pupils with high school background so that they can make their college courses or their technical or professional education complete. Libraries for the Blind It is now much easier and considerably less expensive to have important w'orks in the education of the blind recorded, and one may have as many copies made of the sound film as desired. In libraries for the blind an acoustical library would include a much greater variety of books than is possible with the present method of Braille writing or any other method, and it would make, in a great many instances, the special service of a reader unnecessary. The state department of education could make savings in this line and at the same time intensify this important service for blind pupils. Incidentally, it would be easier to assemble this acoustic library in the form of a few light rolls which also can be fitted more easily into the limited space of libraries than books, heavy and large in Braille writing. Thus, the introduction of this '"Talking Book" may soon become a valuable tool in the furtherance of human welfare and civilization. Fig. 1. Close-up of the film-playing phonograph.