Implementation Of A Narrowband Active Noise Control System Frequency Mismatch Compensation Method

As a complement to passive noise control, active noise control method is effective in suppressing low frequency noise. There are two main directions of active noise control: the broadband and the narrowband, whose target noise frequency spectrum are continuous and discrete, respectively. Here we mainly cover the narrowband active noise control system, aiming to develop a method to deal with the problem of frequency mismatch. The narrowband active noise systems employ a non-acoustic sensor, such as voltmeters and accelerometer, to measure the frequency components of the primary noise. However, due to temperature changes and aging, etc., the measured frequencies may not necessarily reflect the nature of the primary noise. Serious performance downgrade of the narrowband active noise system will occur because of such frequency mismatch.In the paper, a new frequency mismatch compensation method based on auto-regressive model is proposed. Detailed comparisons are made between the new method and existing ones. Simulations on matlab and experiments on DSP platform confirm the effectiveness of the proposed method. The main content of the paper are as follows:(1) The basic active noise control theory and the most widely used algorithms.(2) By analyzing the working of narrowband active noise control system, problems, such as on-line secondary path estimation, frequency mismatch and non-linearity of the pipe, are pointed out. Describing two existing solution for the frequency mismatch: the minimum variance distortion-less response based method and the auto-regressive based frequency tracking method. Analyzing their cons and pros.(3) Put forward the auto-regressive based frequency estimation method, giving out the distinctive feature of the new method in comparison with above two method. The later part of the paper covers the programs an d experiment set-up for the method.(4) Reveal the strong and weak points of these methods with simulations and experiments. The new method signifies itself with a strong resistance to non-stationary noise. The non-linearity of the pipe is commented.