Abstract
A resonance tube system has been used to study the propagation of sound in mixtures of gases. The resonance tube consisted of a long duralumin tube terminated at one end by a fixed reflector and at the other by a plane diaphragm. The diaphragm was vibrated by a moving coil at an amplitude determined by an optical system using a laser, and the variation with frequency of the driving point impedance of the diaphragm-gas-column system was investigated in the neighbourhood of several natural modes of the tube. A computer was used to evaluate the sound attenuation and velocity from these measurements. Measurements were made in oxygen containing up to 0.25% water vapour at six different temperatures in the range 298K to 410K, and in oxygen with up to 13% helium at 296K. These results are listed in the table below. In addition sound attenuation and velocity measurements were made in pure dry oxygen in the temperature range 298K to 410K. From these measurements the Helmholtz-Kirchhoff coefficient was calculated and was found to be about 30% higher than the theoretical value. This difference increased with increasing temperature.