Structure design of low-frequency broadband sound-absorbing volute for a multi-blade centrifugal fan

Abstract

A novel low-frequency broadband sound-absorbing structure is proposed for the noise reduction of an existing multi-blade centrifugal fan in range hoods. Incorporating the advantages of both sound absorption materials and micro-perforated panel absorbers in series and in parallel with unequal cavity depths, the compound absorber is designed to suppress and absorb the radiated noise mainly in the wide- and low-frequency range below 2 kHz. Parametric studies for influences of structural parameters on sound absorption coefficient and absorption bandwidth are performed with numerical method, respectively for sound absorption materials and micro-perforated panel absorbers in series and parallel arrangements. Due to the non-uniform directivity of far-field sound radiation, the optimal installation position of the compound sound-absorbing structure at the volute, the helical surface or the two lateral side planes, is investigated as well. Taking the actual structures of the centrifugal fan, special working environment of the range hood, processing cost and difficulty into consideration, a practical low-frequency broadband compound absorber with an elaborate selection of structural parameters is designed and applied to the appropriate positions. Results of the acoustic test in the anechoic chamber according to the Chinese national standard indicate that the A-weighted sound power level on the monitoring spherical surface meets the acoustic target of lower than 64.0 dB(A) under restrictive conditions of large flow rate, high pressure and small size.