On the phase difference of the temperature and pressure waves in the thermoacoustic effect

In this comment, the single-plate, linear theory for the thermoacoustic phenomenon in ideal conditions, Prandtl Number (σ) zero and a plate with infinite heat capacity, presented by Swift 1] has been used to find expressions for the phase difference α between the temperature and pressure waves. The effect of Prandtl Number different from zero and a plate with a finite heat capacity has also been analyzed. It has been found that the behavior is governed by the relation between a non-dimensional temperature gradient Γ and σ. Attenuation occurs for Γ < 1 + √σ and excitation for Γ > 1 + √σ which correspond to |α| < π/2 and |α| > π/2 respectively. Explicit expressions for a as a function of the transverse coordinate are given. A physical interpretation of the results is presented in the context of concepts offered by Lord Rayleigh.