Attenuation Effects of Discrete Tone Using Adaptive Feedback Active Noise Control

The attenuation characteristics of a slit resonator that combined the adaptive feedback ANC system at a ventilation aperture of the package for leakage noise is investigated. The discrete tones radiated from an AC axial flow fan are controlled by DSP using Filtered-X Least Mean Square algorithm. The attenuation is found at the range of: 3dB-14dB with circular slit resonator, 2dB-15dB with elliptic slit resonator. Results of measurement show that the proposed system can achieve TNR(Tone to Noise Ratio) and PR(Prominence Ratio) under threshold effectively.