Abstract:
Proper impedance model is important to the design of perforated-panel lining. Several widely-used impedance models under grazing flow in literatures vary considerably. Due to the difference between measurement methods, acoustic impedance measurement results differ much from each other, which cause difficulties in direct comparison of impedance prediction models based on measurement results.The transmission losses (TL) of perforated-panel lining under grazing low at different speeds are adopted to compare 6 selected different impedance models and 30 combined models composed by acoustic resistance part and acoustic reactance part of the 6 models. TL can be obtained from the four-pole parameters calculated by the transfer element method. Results show that at low-medium frequency, sound transmission loss obtained from 6 acoustic impedance model in references agree well with measurement results, while at high frequency there exists remarkable deviation between calculation results and measurements. The combination model of the resistance part of Lee & Ih model and the reactance part of Cummings model matches best with the measured results at the flow speed not higher than 0.2 Ma.
