Investigation of flanking sound transmission in lightweight building structures using a scanning laser vibrometer

In some cases the overall sound transmission between adjacent dwellings is governed by flanking transmission and hence testing of the flanking performance of building structures is an important issue. Usually the well established indirect measurement method of ISO 10848 is applied for testing junctions of lightweight building elements like wood joist floors and gypsum board walls. Here a full-scale junction is built in a special test facility, some surfaces of the test specimen are shielded, and the sound pressure level difference between the source and receive rooms is measured. An estimate of the flanking sound reduction index of one particular path is obtained by considering the power injection, propagation attenuation of structural waves in the two coupled elements, junction attenuation, and radiation into the receiving room. In this paper a scanning laser vibrometer is used to get a better understanding of flanking transmission in lightweight building structures and of the above-mentioned mechanisms. The spatial distribution of the velocity on the surface of the structure is measured and structural power flow is investigated.Dans certains cas, la transmission acoustique globale entre logements contigus est tributaire du ph\ue9nom\ue8ne de la transmission indirecte; de l\ue0, la mise \ue0 l?essai de la performance des structures de b\ue2timent en termes de transmission indirecte demeure une question importante. Habituellement, la m\ue9thode de mesure de la transmission indirecte bien \ue9tablie de la norme ISO 10848 est indiqu\ue9e pour mettre \ue0 l?essai les jonctions d?\ue9l\ue9ments de construction l\ue9gers tels que les planchers \ue0 solives de bois et les murs en plaques de pl\ue2tre. Nous avons b\ue2ti ici une jonction en vraie grandeur dans une installation d?essai sp\ue9ciale; certaines surfaces du sp\ue9cimen d?essai sont prot\ue9g\ue9es d?un \ue9cran, et l?on mesure l?\ue9cart des niveaux de pression acoustique entre la pi\ue8ce source et la pi\ue8ce r\ue9ceptrice. On en arrive \ue0 une estimation de l?indice de r\ue9duction du son transmis indirectement d?un trajet de bruit en particulier en prenant en compte l?injection sous pression, l?att\ue9nuation de la propagation des ondes structurales dans les deux \ue9l\ue9ments coupl\ue9s, l?att\ue9nuation de la jonction, ainsi que le rayonnement \ue0 l?int\ue9rieur de la pi\ue8ce r\ue9ceptrice. On emploie ici un vibrom\ue8tre \ue0 laser de lecture dans le but de mieux comprendre la transmission indirecte dans les structures de b\ue2timent l\ue9g\ue8res ainsi que les m\ue9canismes susmentionn\ue9s. La distribution spatiale de la vitesse des ondes sur la surface des structures est mesur\ue9e, et la cha\ueene cin\ue9matique structurale, \ue9tudi\ue9e.Peer reviewed: YesNRC publication: Ye