Absorption coefficients measured in reverberation chambers, Sabine absorption coefficients, suffer from two major problems. Firstly, they sometimes exceed unity. Secondly, the reproducibility of the Sabine absorption coefficients is quite poor, meaning that the Sabine absorption coefficients vary largely depending on the test room. Several conversion methods for porous absorbers from the Sabine absorption coefficient to the random incidence absorption coefficient were suggested by considering the finite size of a test specimen and non-uniformly incident energy onto the specimen, which turned out to be successful in terms of the trueness. However, the reproducibility of the converted random incidence absorption coefficients has not been investigated. The present study mainly focuses on the reproducibility of the random incidence absorption coefficients that are converted from the Sabine absorption coefficients measured in 13 different chambers in a recent round-robin test, revealing that the reproducibility of the converted random incidence absorption coefficient is improved significantly compared to that of the Sabine absorption coefficient. Between the two optimization methods used, the flow resistivity optimization outperforms the surface impedance optimization in terms of the reproducibility.
Acustica United With Acta Acustica, 2015, Vol 101, Issue 1, p. 99-112