Experimental energetic analyses of an actively controlled one-dimensional acoustic waveguide

Abstract

Technological development has made it possible to implement digital active noise control systems in real time. This work compares the performance of different adaptive control methods applied to a one-dimensional waveguide. The compared control methods are the frequency-domain filtered-X LMS using potential energy density and kinetic energy density as cost functions, and the active sound intensity control (ASIC), which uses active intensity as the cost function. The ASIC controller is implemented with both the P–U approach (measuring pressure and particle velocity at the same time) and the P–P approach (using two microphones to estimate the active intensity). The waveguide is a circular PVC duct with a primary source placed at one end, the secondary source placed near the mid-span of the duct, and with an open-ended termination. The analyses were performed comparing the results in terms of the potential energy density, the active intensity, and the acoustic power radiated by the sources. Moreover, it is shown how to choose suitable error sensors and their influence in the performance of the ASIC controller. The results show that the control methods achieved the same final result and, as expected, when the volume velocity of the secondary source was driven to the optimal volume velocity, the primary source and the secondary source radiated less acoustic power than the uncontrolled primary source. Besides, the sound intensity was effectively attenuated throughout the duct.