The drying process influence on the brick walls sound reduction index: Laboratory evaluations and theoretical analysis

This paper presents the experimental results concerning the sound reduction index of different types of brick walls; the analysis was in particular carried out on double walls, single walls and single walls with external lining. Its main purpose is to find the minimum drying time of the structure necessary to obtain the sound reduction index of brick walls as close as possible to actual laboratory values. Moreover, it aims at making results of different laboratories as comparable as possible in terms of repeatability and reproducibility. All the fundamental quantities, such as sound reduction index (R), weighted sound reduction index (Rw), spectrum adaptation terms C and Ctr, have been analyzed, and temperature (T) and relative humidity (R.H.) in the receiving room, have been recorded. A qualitative analysis of the curves slope of the sound reduction index versus frequency has been conducted for each drying time and each type of examined wall. The measurements were carried out in the acoustics laboratory of ITC-CNR (the Construction Technologies Institute of the Italian National Research Council) in Milan, according to the procedures set out in ISO 140 part 3.