Analysis of low frequency sound and sound induced vibration in a Norwegian wooden building

Low frequency sound, in addition to the effects of audible sound, contributes to human annoyance and building damage by inducing building vibration. This involves whole body vibration sensing of humans, and therefore frequencies down to a few Hz become important. Here, the results of a study of low frequency sound and its generation of building vibration and induced indoor sound is presented. The study is conducted by combining both full scale field tests and numerical simulations. It is shown that the low frequency sound interaction with the fundamental frequencies of the building components combined with air leaks in the building envelope are the main factors that govern transmission of sound into the building. Furthermore, radiation from vibrating ceiling and walls seems to be the dominant source of the low frequency indoor sound, and floor vibration is acoustically driven by the indoor sound pressure in the room. Due to the low frequencies in question, tools to predict sound and vibration, and design mitigation measures at low frequencies noise and vibration in building structures are virtually non-existent. To this end, a finite element model combining acoustic wave propagation and structural dynamics presented in this paper provides a first step. Using this model, a number of countermeasures has been tested and some proven effective in this low frequency range.