Abstract
The push for greater urban sustainability has increased the urgency of the search for noise mitigation solutions that allow for natural ventilation into buildings. Although a viable active noise control (ANC) solution with up to 10 dB of global attenuation between 100 Hz and 1000 Hz was previously developed for an open window, it had limited low-frequency performance below 300 Hz, owing to the small loudspeakers used. To improve the low-frequency attenuation, four passive radiator-based speakers were affixed around the opening of a top-hung ventilation window. The active control performance between 100 Hz and 700 Hz on a single top-hung window in a full-sized mock-up apartment room was examined. Active attenuation came close to the performance of the passive insulation provided by fully closing the window for expressway traffic and motorbike passing noise types. For a jet aircraft flyby, the performance of active attenuation with the window fully opened was similar to that of passive insulation with fully closed windows. In the case of low-frequency compressor noise, active attenuation’s performance was significantly better than the passive insulation. Overall, between 8 dB and 12 dB of active attenuation was achieved directly in front of the window opening, and up to 10.5 dB of attenuation was achieved across the entire room.
Highlights
The World Health Organization (WHO) has recently put forth strong recommendations to reduce urban transportation noise levels
Each primary noise type was played on loop to allow the filtered-x least mean square (FXLMS) algorithm to converge to a steady state, after which the control filter coefficients were stored
The control signals were generated by convolving the reference signal with the stored fixed-coefficient finite impulse response (FIR) filters, i.e., yk (n) = wTk, f ixed (n) ∗ x(n), where wk, f ixed (n) is the kth fixed-coefficient control filter
Summary
The World Health Organization (WHO) has recently put forth strong recommendations to reduce urban transportation noise levels. These recommendations are underpinned by a rapidly growing body of evidence associating a myriad of health risks with environmental noise exposure [1]. Noise mitigation at the receivers’ end, such as on building façades, is inefficient, it is usually the only form noise control available for land-scarce, high-density urban cities. The sustainability push for naturally ventilated buildings increases noise control difficulty, as noise propagates through any opening in the façade. Noise control for naturally ventilated buildings has been traditionally passive, wherein physical elements have been employed to obstruct or dampen the acoustic waves as they enter the façade [3,4]
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