An annular plenum is integrated downstream of six pulse detonation combustors arranged in a canannular configuration. The primary purpose of the plenum is the mitigation of pressure and velocity fluctuations, which is crucial for operation with a downstream turbine. The flow inside the plenum is investigated by means of flush-mounted pressure transducers arranged in the axial and circumferential directions. The test rig is operated in different firing patterns at 16.7 Hz per tube. Two firing patterns are studied to characterize the shock dynamics inside the plenum. The obtained data allows for a better understanding of shock interaction and attenuation inside the plenum, as well as the quantification of pressure fluctuations at the plenum outlet. Furthermore, a comparison is made between piezoresistive and piezoelectric pressure transducers, showing the capability of piezoresistive transducers for dynamic pressure measurements. The performance of the piezoresistive transducers allows for time-resolved measurement of both static and total pressure at the exit of the plenum. Moreover, the plenum results in a significant attenuation of the leading shock wave while redistributing its energy both spatially and temporally.