Weatherproof resonator array for low frequency noise reduction through open windows

Natural ventilation improves indoor air quality but also allows external noise, especially in urban areas where traffic noise can be around 75-85 dB. A previously developed resonator array, designed to reduce transmitted noise while maintaining over 70% open area, achieved a 10-12 dB reduction in the 400-600 Hz range. This study enhances that design by introducing a waterproof cloth cover with a 5 mm air gap at the resonator mouth for weather protection. The resonators are designed and analysed using MATLAB and COMSOL, then fabricated and tested as an array. Individual resonators were tested in an impedance tube before array testing in a reverberation chamber with a 465 × 465 mm opening. The array consists of resonators tuned to four different frequencies spanning the range of 400-600 Hz. The array showed 10-14 dB reductions around each resonator frequency, while 1/3 octave band analysis showed over 6 dB reduction for the 400 Hz and 500 Hz bands. Airflow tests were done to simulate real-world wind conditions, demonstrating a 5-6 dB reduction across both bands. These results confirm the array's effectiveness for urban noise control. Future work will focus on optimising resonator designs to target additional octave bands for broader noise reduction.