A 2-cm and 3-cm stack length has been studied to look at the acoustics generated from a heat source generated by a
propane torch. The source is placed before the opening of the hot-side duct of Fig 1. No hot heat exchanger is used with the
heat being directed straight to the stack [13]. The ambient heat exchanger was fabricated from thin copper plates, the
dimensions of which are 10 mm by 50 mm with a thickness of 1mm (Fig 2b). The heat exchanger was cut into a 50-mm
diameter and positioned next to the Celcor stack within the duct. Four K-type thermocouples are used to measure the
temperatures at the mouth of the resonator (T1), before (T2) and after the stack (T3), and the end of the resonator (T4). A type
26AH microphone amplifier is located at the closed end for measuring the local pressure deviation from the ambient.