Noise control for a dipole sound source using micro-perforated panel housing integrated with a Herschel–Quincke tube

This study presents a passive noise control approach for directly suppressing sound radiation from an axial-flow fan, which involves micro-perforated panels (MPPs) backed by cavities and integrated with a hollow tube with the characteristics of a Herschel–Quincke (HQ) tube (MPPHQ housing). Noise suppression is mainly achieved by sound cancellation between the sound fields from the fan with a dipole nature and sound radiation from a vibrating panel via vibro-acoustic coupling. In addition, noise mitigation is supplemented by sound absorption in micro-perforations and acoustic interference at the hollow tube boundaries. A two-dimensional theoretical model is established to investigate the HQ segment housing a sound source. Results show that the HQ segment enhances the sound suppression performance in the passband region of the MPP housing device, and thus, a widened effective working band is obtained. Optimization is conducted to identify the optimal parameters for the MPPHQ housing. The proposed method has the potential to effectively control ducted-fan noise and to enhance the quality of products with a ducted-fan system.