Comments on "Variable Explicit Regularization in Affine Projection Algorithm: Robustness Issues and Optimal Choice

The above paper presented a variable regularized affine projection algorithm (VR-APA). A delay coefficients-based variable regularized affine algorithm (DC-VR-APA) was presented in [2], [3]. It was shown in [1, pp. 2103, (39)] that DC-VR-APA is an equivalent and alternate manifestation of the VR-APA when the affine projection order is equal to 1. However, results pertaining to input speech signals and presence of near-end speech activity 1 were not reported in. For the same set of parameters, this letter 2 shows that DC-VR-APA is more robust to the above conditions than the VR-APA. Motivated by some of the explanations in, we present the reasons for the robustness of DC-VR-APA in the above conditions.