## In-situ/laboratory correlation for sound reflection/absorption over all barrier types

The diagram shows the correlation between measurement results of the laboratory method for sound absorption and the in-situ method for sound reflection over all barrier types available in the database. This correlation is based only on cases where both methods have been used for testing the same barrier. The correlation has been performed for two different frequency ranges. The frequency range where the data were available is specified for each method in the diagram title. The formula of the linear regression is also shown in the diagram. In this case the coefficient of the linear regression indicates a rather good accordance between the two methods. Due to the relatively small number of cases for which results from both methods were available the linear regression cannot represent a robust relation for each barrier material separately. To establish such a relation more data would be needed. However a general trend can be recognised in the diagrams.