Abstract
Shutting the window is usually the last resort in mitigating environmental noise, at the expense of natural ventilation. We describe an active sound control system fitted onto the opening of the domestic window that attenuates the incident sound, achieving a global reduction in the room interior while maintaining natural ventilation. The incident sound is actively attenuated by an array of control modules (a small loudspeaker) distributed optimally across the aperture. A single reference microphone provides advance information for the controller to compute the anti-noise signal input to the loudspeakers in real-time. A numerical analysis revealed that the maximum active attenuation potential outperforms the perfect acoustic insulation provided by a fully shut single-glazed window in ideal conditions. To determine the real-world performance of such an active control system, an experimental system is realized in the aperture of a full-sized window installed on a mockup room. Up to 10-dB reduction in energy-averaged sound pressure level was achieved by the active control system in the presence of a recorded real-world broadband noise. However, attenuation in the low-frequency range and its maximum power output is limited by the size of the loudspeakers.
Highlights
Shutting the window is usually the last resort in mitigating environmental noise, at the expense of natural ventilation
An active noise control (ANC) system is an electroacoustic system, which usually comprises of a ‘reference’ sensor to provide advance information of the primary noise to be attenuated, an actuator driven by an adaptive circuit to produce the anti-noise, and an ‘error’ sensor to provide feedback to the adaptive circuit to adapt to changes in the primary noise
The experimental setup is guided by 2D finite element method (FEM) simulations, which investigated the passive acoustic attenuation provided by full glazing and the active attenuation of an ANC system in combination with sliding glass panels
Summary
Shutting the window is usually the last resort in mitigating environmental noise, at the expense of natural ventilation. We describe an active sound control system fitted onto the opening of the domestic window that attenuates the incident sound, achieving a global reduction in the room interior while maintaining natural ventilation. The incident sound is actively attenuated by an array of control modules (a small loudspeaker) distributed optimally across the aperture. In the context of dense high-rise cities, only the plenum window strategy has shown promise[3,4], but it has yet to overcome its inherent reduction in natural ventilation[2]. Noise propagating through an open aperture can be treated as the source to be controlled, and both the control sources and error microphones could be arranged optimally to achieve global control by minimising the total sound power output of the aperture, as shown in a previous numerical study[15]. Numerical simulations have shown that the boundary-based layout is ineffective for an aperture in a thin rigid wall, i.e. window on the building façade[5]
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