ACOUSTIC LOSSES IN A RESONATOR WITH STEADY GAS FLOW.
Technical rept. no. 2.
BOLT BERANEK AND NEWMAN INC CAMBRIDGE MASS
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Measurements have been made of the acoustic losses in a resonator with a small vent, and their dependence on the speed of steady flow through the system and on the position of the vent. The resonator is a closed circular cylinder, resonant in the fundamental planewave mode, with a vent through the wall near the center. Steady gas flow is introduced at one end through a slightly porous piston whose vibration also generates sound. Losses are determined from the rate of decay of pressure. Significant flow-dependent loss attributable to the vent is found for flow speeds in the vent exceeding about 0.02 times the sound speed. The loss depends on vent position. Good quantitative prediction of this loss, at flow velocities above a critical value, can be made from a theory based on the characteristics of quasisteady fluid efflux from an orifice total pressure quadratic in total flow. Author