The paper examines and discusses possible explanations of the systematic deviations between conventional and intensity-based sound transmission loss measurements frequently reported in the literature. Both the conventional diffuse-field method and the method based on the sound intensity technique are subject to several systematic errors of comparable size. The sources of error include non-linear decay functions, the absorption of the partition itself, and intensity measurement errors, which are aggravated by the fact that the sound field conditions are usually fairly difficult. It is concluded that with very careful measurement procedures there are no systematic deviations.
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