Simple secondary path modeling for active noise control using waveform synthesis

Abstract

Active noise control algorithms for real world applications regularly use some kind of digital filtering and adaptation to compensate for the influence of the secondary path. Such is the FxLMS algorithm with techniques for offline and online estimation of the secondary path, suitable both for broadband and narrowband noise. When silencing periodic noise using waveform synthesis, much simplified solution can be used. Instead of a long adaptive filter, a simple delay can be used. After initial off-line calibration, delay values are stored in a lookup table. These values are used later instead of adaptive filter and may change with the frequency of repeating waveform. It is a simple and intuitive solution that poses some restriction on phase response of used secondary source. Due to the low computational requirements it is suitable for implementation using simple and low cost microcontroller.