The present paper reports on recent work to further understand the properties of Heimholt? resonator Powered Resonance Tubes (PRT). Three different PRT geometries with Heimholt? resonators were examined. For comparison, a single straight tube resonator was also simulated. Simulation results are compared to both theoretical and experimental findings. The simulations were found to be in excellent qualitative agreement with both theory and experiment. The use of Heimholt? resonators as part of a PRT is found to be an effective means of obtaining lower frequency output without requiring as long a resonator chamber as with a straight tube.