Continued Study of Optical Sound Generation and Amplification.

摘要

The general thrust of the research described in this report is acoustics of systems far from the equilibrium. This topic is subdivided into sound amplification and sound generation though the two are very much intertwined. In the case of sound amplification, research is focused on the propagation of sound through a gas which has internal states far from equilibrium. Sound generation as discussed in this report results from depositing energy in an internal state. Calculations show that some very stringent conditions must be met if sound amplification is to be experimentally observed. For the magnitude of the gain to be appreciable, the v-t relaxation time can only be about one order of magnitude longer than the sound period. A number of experimental configurations were tried to meet these conditions. The effect was observed and measured in N2/H2, N2/He, N2/H2O, and N2/CH4 mixtures. Although the basic principles governing optoacoustic generation of sound have been well established for many years, the goal of the work reported here was to use this technique to study energy transfer at the molecular level. This required that all factors influencing the acoustic waveform including vaporization be accurately considered. Keywords; Optoacoustics; Sound amplification; Vibrational relaxation. (kt)