Textile curtains can be designed to be good sound absorbers. Their acoustical performance, as usually described by the sound absorption coefficient, not only depends on the textile itself but also on the drapery fullness and the backing condition, that is, the spacing between the fabric and a rigid backing wall, or the absence of a backing in the case of a freely hanging curtain. This article reviews existing models to predict the diffuse-field sound absorption coefficient, which to date can only predict the case of flat curtains. A set of existing models is extended to the case of curtains with drapery fullness using a semi-empirical approach. The models consider different backing conditions, including freely hanging curtains. The existing and new models are validated by comparing predicted sound absorption coefficients with data measured in a reverberation room. Hereby, curtains consisting of different fabrics and with different degrees of fullness are considered. Besides situations with rigid backing, also the measurement data of textiles hung freely in space are included in this study. Comparisons reveal a very good agreement between measured and predicted sound absorption coefficients. Compared to currently available commercial sound absorption prediction software that can only handle the situation of flat textiles with rigid backing, the results of the presented models not only show a better agreement with measured data, but also cover a broader range of situations. The presented models are thus well applicable in the design and development of new textiles as well as in the room acoustical planning process.
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NRC Publications Archive Archives des publications du CNRCThis publication could be one of several versions: author's original, accepted manuscript or the publisher's version. / La version de cette publication peut être l'une des suivantes : la version prépublication de l'auteur, la version acceptée du manuscrit ou la version de l'éditeur. For the publisher's version, please access the DOI link below./ Pour consulter la version de l'éditeur, utilisez le lien DOI ci-dessous.http://dx.doi.org/10.3813/AAA.918439 Acta Acustica United with Acustica, 97, 4, pp. 590-598, 2011-07-01 Prediction of the blocked force at impact of Japanese rubber ball source Schoenwald, S.; Zeitler, B.; Nightingale, T. R. T. Abstract: Characterizing and rating the impact sound isolation of floors and of building structures are important issues in building acoustics. In all standardized test procedures a floor specimen is excited structurally with a standardized impact source and the sound pressure level due to the impact is measured in an adjacent room. Existing standards define several impact sources that should simulate the excitation due to persons walking or jumping on the floor and hence exert only normal forces to the structure. However, the excitation spectrum of the most commonly used lightweight tapping machine according to ISO 140-7 differs significantly from the heavy impact sources according to JIS A 1418-2 (the "rubber ball" and the "bang machine" that are dropped from a defined height to the floor). In order to accurately predict the impact sound isolation of floor assemblies, the excitation mechanism due to impacts from these heavy sources has to be understood and implemented in prediction models. This paper presents a simple analytical model for the "rubber ball" heavy impact source and the suitability of the model is gauged by comparing the predicted blocked force with experiment.
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