The effect of gas density on the acoustic properties of a turbulent jet

The acoustic properties of nonisothermal air jets and isothermal jets of helium and carbon dioxide outflowing into air were studied experimentally. The effect of the gas density on the acoustic power, acoustic directional characteristic, and noise spectrum of a turbulent jet was investigated. It is shown that density gradients produce additional noise sources in monopole and dipole jets. Variable density jets are found to generate noise more efficiently than constant density jets at low jet velocities.