Sounding Systems for Public Air Raid Warning

Abstract

One of the essential parts of the United States Air Raid Warning System is an outdoor sound-signal system for public warning. These sound signals are intended to reach people who are out of doors or are in the external rooms of buildings at the time the warning is sounded. It is anticipated that additional supplementary signals will be required for stores, theaters, factories, public buildings, etc. It is common experience that whistles and other noises from trains, boats, etc., are heard for miles under favorable conditions such as exist on quiet summer nights. It is equally common experience that under more usual conditions, loud sounds are seldom heard for more than a few blocks. In fact, this experience is so common that it is usually forgotten. When sounding systems for air raid warnings were first contemplated a few months ago, it was thought that adequate coverage could be obtained by means of a few horns, sirens, or whistles. Initial tests with such equipment were uniformly disappointing. Accordingly, the United States Office of Civilian Defense undertook to determine what would be required for a practical air raid sounding system, and to make this information available to the communities responsible for installing such equipment. A number of organizations have participated in this work, and the technical information obtained will be presented by representatives of these organizations. The present paper describes how these various efforts were correlated.