First Numerical and Experimental Results on Active Controlled Glazed Facades

Abstract

Both recent legislation codes and the evidence of the effects of high noise levels on human health have directed research activities towards the problem of the improvement of Sound Transmission Loss (STL) of glazed facades in the frequency range (low-medium) where passive means were already shown to be not effective. Adopting active control systems may help to cover the lower set of frequencies, where traffic and railway noise produces high level of disturbance. In this paper it is shown how Piezoelectric (PZT) stack actuators may be installed on large curtain walls, improving their STL. They are demonstrated to be particularly useful to avoid drops of STL in correspondence of resonance frequencies of windows, hence increasing their overall STL. Some simulations on the noise reduction obtained inside a standard building enclosure were performed, comparing the noise transmitted by a standard window with the corresponding active controlled one and several technologies for the installation of PZT actuators are suggested.

An Active Technology for Improving the Sound Transmission Loss of Glazed Facades

“…In previous research activities simulations have been led to evaluate achievable noise level reduction by the application of the ASAC technique, without considering the influence ascribable to the presence of a stiffener or a stiffening mass for the correct functioning of the actuator. In the above case, a reduction of about 15 dB in the disturbance pressure noise was estimated (Naticchia & Carbonari, 2006). Results of simulations presented in this paragraph instead, can be considered more realistic, as it also takes into account the presence of the stiffener.…”

“…This choice was influenced by the two following considerations: -maximum structural response is recorded when a system is excited close to its natural frequencies; -for the assumed control theory, maximum efficiency is obtained controlling modes with the maximum acoustic efficiency. From previous studies (Naticchia and Carbonari, 2006), it is possible to establish that they are coincident with the glass panel's natural frequencies, with particular reference to (3,1) and (1,3) modes. For experimental measurements the same apparatus described in paragraph 6.2 was employed, with exception of PXI platform, replaced by the National Instruments Acquisition Card depicted in Fig.…”

Design and Development of an Active Controlled Window with High Sound Transmission Loss

“…In Ref. [3] it was shown also that 1 or 2 actuators are enough to properly control acoustic vibrations of glass: preliminary simulations showed that, according to the theoretical behavior of windows subject to acoustic excitations and controlled by one or two point forces, it is possible to reduce noise re-irradiation up to 15 dB. However in that case the real behavior of controlling actuators was approximated with point forces, neglecting further disturbances to glass panels, due to the stiffening structure they need work.…”

“…[2] presents a full description of all the active approaches presently available, whose basic subdivision states between: Active Noise Control (ANC) and Active Structural Acoustic Control (ASAC). The authors have already explained in other contributions [1,3] that the first is not suitable for the purpose of improving windows' STL because it is based on the production of a cancelling wave that interferes destructively with the disturbing one: it means that some loudspeakers and microphones need to be installed in the receiving environment, and that their functioning should change according to the room shape and to the presence of people, that is clearly not feasible. For that reason the ASAC one was adopted for controlling glazed facades, which is performed by changing the vibration field of structures radiating noise.…”