Article

The theoretical fundamentals of an adaptive active control using periodic Helmholtz resonators for duct-borne transmission noise in ventilation systems Y Yun and CM Mak This article theoretically proposes an innovative semi-active noise control method for the control of duct-borne transmission noise. This method is designed to be a more efficient, robust and broad-band adaptive attenuating effect than the traditional pass noise control methods used in duct-borne sound control. Based on the fundamental theory on the pass-stop band structure of sound waves propagating in a one-dimensional periodic duct system, the proposed control method combines band-gap attenuation using the side-branch resonators array with the auto-adaptive system of noise control. Using this method in the simulation and analysis, the transmission noise in an air duct can be effectively controlled in relatively wide bands by periodic alternate resonators of small variable parameters. The developed semi-active control method is numerically designed to efficiently reduce the duct-borne transmission noise at frequencies around a variable major tone in various working conditions. Practical applications: The proposed semi-active noise control method with band-gap attenuation of a periodic adaptive resonator array is generally an efficient, robust and broad-band noise control system. It has the potential to be used to control duct-borne transmission noise in order to satisfy stringent indoor acoustical requirements such as those of the indoor air-conditioned environments of a hospital, a scientific laboratory, a council hall and a living room