Audible electric signals in industrial plants, and acoustical engineering

The paper is a plea for a wider use of acoustic signals in industrial plants. It is shown that much time is wasted by the officials, experts, and important employees in trying to locate each other. With loud acoustic signals installed throughout a plant, in the shops, yards, and offices, it becomes possible to locate any of a considerable number of men instantly, using a simple code call for each. Such calls could be given only imperfectly by pushing a button, and for this reason a special code calling instrument has been developed, which closes electric contacts automatically, after having been set for a desired combination. The actual conditions and the needs for acoustic signals are discussed in application to steel mills, shipyards, textile mills, printing establishments, coal mines, construction jobs, etc. It is shown that in addition to code calls, audible signals and particularly electric horns are used with advantage as extensions to telephone bells in noisy places, and also as warning signals for various purposes. The general scope of the forthcoming art of acoustic engineering is then discussed, and its importance is shown in design of theaters, churches, and large auditoriums; also in the installation of fog signals. The problem of measurement of sound intensity is then taken up and the available means and devices are described. It is also shown that sound waves may be directly photographed under proper conditions and the laws of their propagation studied. Attention is called to the importance of experimental and theoretical study of the modes of vibrations of diaphragms used in acoustic devices.