Noise cancellation system based on active noise control. 2nd Report, Adaptive control method.

The active noise cancellation technique has been developed recently. When a system characteristic, i.e., transfer function, changes, we must also change the coefficients to cancel the noise. In that case, we should utilize the adaptive control technique. This paper describes the problem when using the adaptive control technique. A solution to this problem was considered by developing a simulation system with acoustic characteristics. We determined that the adapting process had a different characteristic of convergence according to signal periodicity. Finally, good agreement was obtained with experimental results of applying this solution to a rather short duct.