Feasibility analysis of an active technology to improve acoustic comfort in buildings

In buildings, windows and glazed facades are often the preferred noise path for exterior disturbing noise towards the interior. Since passive means for improving sound transmission loss (STL) of glazed facades are very expensive and are effective only at high frequencies, an active controller that increases the STL in the low-frequency range is an attractive approach for reducing the noise level in buildings with glazed facades, guaranteeing the performance required by the 89/106/CEE European Directive, which made protection against noise a compulsory requirement for buildings. As buildings are often inserted in highly inhabited urban areas, near infrastructures and plants radiating high noise levels, the strategic importance of this task is increasing, together with the importance of acoustic comfort inside buildings. This paper concerns a feasibility study on the implementation of an active structural control system for glazed facades, in order to improve their STL at low frequencies. At present, applications for the reduction of noise level inside cars and planes are known. Relative to the use of active structural acoustic control (ASAC) systems, these systems are based on the reduction of structural vibrations through the use of actuators bonded on the vibrating surfaces, driven by an automated control system, whose task is minimizing those vibrations, and the radiated sound as a consequence. In this work, it is shown that actuators bonded on the vibrating surfaces, driven by an automated control system, are able to dramatically reduce those vibrations and, consequently, the radiated sound. The proposed technology is tested through experiments and numerical simulations, in order to compute the reduction of interior noise that could be pursued through the use of piezoelectric stack actuators.