Thermoacoustics have a key role to play in energy harvesting systems, exploiting a temperature gradient to produce powerful acoustic pressure waves. As the name suggests, thermoacoustics is a blend of two distinct disciplines: thermodynamics and acoustics. The field encompasses the complex thermo-fluid processes associated with the compression and rarefaction of a working gas as an acoustic wave propagates through closely stacked plates in the regenerator of a thermoacoustic device; and the acoustic network that controls the phasing and properties of that wave. Key performance parameters and appropriate figures of merit for thermoacoustic devices are presented with particular emphasis upon the critical temperature gradient required to initiate the acoustic wave and the thermal properties of the key component, namely, the “stack” or “regenerator". Mechanisms for coupling a thermoacoustic prime mover with electromagnetic harvesters and piezoelectric transducer materials are also presented, which offer the potential to enhance the energy density attained beyond that possible with linear alternators. Numerical modeling strategies are presented, which enable parametric sweeps of the geometric and thermal properties, which influence the efficiency, and performance of the key components of such devices. Potential coupling and non-linear effects are examined.