Production of vibrations by means of solid carbon dioxide

Abstract

The thesis gives a concise account of investigations, which are more fully described in the publications which accompany it, on the subject of the production of vibrations by means of solid carbon dioxide. The circumstances which led to the discovery that pure loud notes could be produced from metallic bodies by means of the substance are described. Certain properties of solid carbon dioxide which are relevant to the investigation are considered. An account of the technique, which took some months to perfect, is given. Frequencies of vibration were measured with a calibrated valve-oscillator. Bodies excited by solid carbon dioxide, besides possessing adequate vibrating properties must be reasonably good thermal conductors. It is possible to produce intense vibrations in quartz crystals and bars in addition to metal objects. Semi-conductors may be distinguished from Insulators by the fact that the former only emit a sound when touched with solid carbon dioxide. The range of vibration frequencies most easily excited depends but little upon the size, shape, mass, material or heating of the excited body; it lies between about 1000 and 4000 c./sec. A theory to account for the phenomenon is given in the paper. Metallic bodies, heated to suitable temperatures, have also been set into vibration by means of ice and certain other materials; only small amplitudes of vibration have been obtained in this way. There are a number of applications of the solid-carbon-dioxide method of excitation. Of these, mention may be made here of the production of Chladni figures on plates and of overtones in bodies of Irregular shape. A simple method of measuring Poisson's ratio in terms of the ratio of two specified natural frequencies of a vibrating free square plate and the results of acoustic studies of metals and alloys under various physical conditions are also included among the publications.