Medição de isolamento sonoro pelo método da função de transferência

Abstract

One important characteristic for a good acoustical performance in a room is the sound isolation between rooms, so that the sound field in a room won’t suffer interference of external sound fields. In the present work experimental methods to assess the in-situ sound isolation are studied. The primary goal is to evaluate the transfer function method, an alternative to the most commonly used method, described in the ISO 140 and NBR 15575. These method is based on a consolidated theory and is vastly used in many applications mainly in electrical engineering. According to studies in acoustics, the method features better signal-to-noise ratio, less influence of background noises and sound source distortions, obtaining thus greater reliability and precision comparing to the traditional method. A question that still must be investigated for this method is the complete determination of its measurement uncertainty. To initiate the study of this issue the most primary components of uncertainty were identified and a procedure for its calculation was adopted. Tests in different experimental conditions were performed, aiming to test the methods in adverse conditions. The results obtained by in these conditions enabled the methods to be compared, through the standardized level difference and the measurement uncertainty. In this initial study, it was demonstrated that the transfer function method shows results that are equivalent or in some cases better than the traditional method. Besides, as an additional result, some considerations relevant for the final measurement results concerning the methodology applied to the transfer function method ,were done.