An investigation of parametric array loud-speakers for active noise control in a L-shaped duct

In order to solve the problem that the acoustic feedback cause the raise of the complexity of the system and computation of algorithms in active noise control of ducts, the parametric array loudspeakers are introduced as the secondary source in this paper. The high directivity sound beam helps parametric array loudspeakers reduce the acoustic feedback. In order to verify the method, active noise control experiments of parametric array loudspeakers using as a secondary source in L-shaped ducts have been completed for single frequency noise and bifrequency noise. Furthermore, regions and areas of noise attenuation have been measured. The experimental results show that the acoustic feedback becomes smaller for parametric array loudspeakers using as the secondary source. Without using feedback compensation, the noise reduction of parametric array loudspeakers is equal with coil loudspeakers' for the single frequency noise; whereas it is relatively imperfect for the bifrequency noise. The noise reduction regions are the entire downstream duct from error microphone, and the noise reduction areas cover the cross-section of the duct. The experiments demonstrate that the noise reduction effectiveness is well and the complexity of the system and computation of algorithms are reduced, under the condition of the parametric array loudspeakers used as secondary source.