flow rate of the exhaust stream 32 through the passageway 72 must accelerate which reduces a static pressure of outlets of the firing tubes 12 this in turn increases a dynamic head of the exhaust stream 32 within the attenuator 40 which reduces a pressure gradient between the exhaust stream 32 within the attenuator 40 and the oxidant and fuel within the firing tubes 12 this facilitates a required firing tube 12 fill rate and will also prevent any back flow of the exhaust stream 32 within the attenuator 40 into or adjacent the outlet ends 28 of the firing tubes 12 therefore the present pde with the scroll ejector attenuator 40 collects the highly unsteady combined flow of exhaust streams 32 passing out of the firing tubes 12 along with any bypass cooling air and delivers this flow to the turbine 30 in a state that will allow the turbine 30 to operate effectively the scroll ejector attenuator 40 mixes the flow of the exhaust streams 32 with a low total pressure loss while attenuating the unsteadiness of any shockwaves within the streams 32 while maintaining a low static pressure at the firing tube 12 outlets to facilitate a high rate of pulsed filling of the tubes 12.