Thermoacoustic oscillations in a cylindrical duct is a classical problem, where in the absence of a temperature gradient, thermoviscous effects simply dampen the propagating acoustic waves. With an imposed temperature gradient, however, these acoustic waves can amplify, which forms the basis for thermoacoustic engine designs. Although attractive within the purview of promoting a “green design”, as these engines have zero emissions, their thermal efficiencies have not been spectacular, especially for some of the more practical designs. We took up this work to understand details of the underlying hydrodynamic mechanisms that govern the conversion of thermal fluctuations into acoustic energy, thereby effectively deciding on the overall efficiencies of these devices.