Measurement of Acoustic Resistance at Sound-Pressure Levels to 171 dB

Absorbing liners, consisting of arrays of acoustic resonators, are being used successfully to suppress combustion instability in rocket and air-breathing engines. For the design of acoustic liners, information is needed on the variation of acoustic resistance with sound pressure at levels above the linear regime, i.e., approximately 100 dB (re 0.0002 μbar). In the work reported herein, a standard impedance tube driven by a high-intensity sound generator was used, along with an improved data-recording technique, to measure the resistance of Helmholtz-type resonator arrays. Incident sound-pressure levels of 171 dB were obtained, which represents an 11-dB increase in sound level over that reported by another investigator in an earlier, similar experiment. A simple correlation of the nonlinear resistance effects with sound pressure is presented.