The city environment can expose populations to excessive noise levels, especially in areas close to transport infrastructure. Transport noise is difficult to control due to its strong low-frequency content, which readily transmits through building envelopes unless these are made very thick and heavy.
A common approach in some industries to control sound and vibration is to perform active control at low frequencies and to let the materials passively control high frequencies. Enhancing glazed windows with a transparent active control system would allow attenuation of sound energy during its transmission through the glazing before it enters the building. This project investigated the feasibility of an active sound control system for glazed façades and explored the available technologies – and the soon-to-be-available systems.
Research publications on active sound transmission control systems for multiple-panel structures are scarce.
Four technologies have been identified and assessed as potential candidates for active control of sound transmission through glazed façade elements:
- loud speakers integrated in the cavity, within the frame
- systems using transparent piezoelectric vibration actuators, on the glass
- transparent thin electro-active polymer film loudspeakers, on the glass
- adaptive Helmholtz resonator, within the cavity.
Each technology has its own strengths and weaknesses: sometimes performance can be increased at the expense of transparency, or vice versa.
The most promising technologies of the four reviewed are considered to be the thin film system and piezoelectric actuators.
All the technologies reviewed are potentially viable solutions for controlling transmission of sound through glazed facades, subject to further research and development.
None is currently ready to be commercialized. They presently stand at different stages of research between pure concept and marketable solution.
An active sound control system at the building envelope can allow better control of sound ingress through building façades and improve quality of life in urban areas, especially in occupied residential and office buildings that are exposed to high levels of external noise.
A sound control system made of smart materials would allow the use of lighter façade constructions.