A frequency-domain nonlinear echo processing algorithm for high quality hands-free voice communication devices

A frequency-domain nonlinear echo processing algorithm is proposed to improve the audio quality during double-talk periods for hands-free voice communication devices. To achieve acoustic echo cancellation (AEC), a real-time AEC algorithm based on variable step-size partitioned block frequency-domain adaptive filtering (VSS-PBFDAF) and frequency-domain nonlinear echo processing (FNLP) algorithm was employed in the DSP chip of the prototype device. To avoid divergence during double-talk periods, normalized variable step-sizes for each frequency were introduced to adjust the convergence speed. Then, the nonlinear suppression function of FNLP was applied to inhibit the residual nonlinear acoustic echo and ensure the good quality of the near-end voice. The results of the experiment with the prototype device show that the proposed algorithm achieved deeper and more stable convergence during double-talk periods compared to the NLMS, FNLMS and traditional PBFDAF algorithms. Less nonlinear acoustic echo in the output was also obtained due to the use of FNLP. A speech quality assessment based on ITU-T P.563 showed that the Sout of the proposed algorithm achieved higher scores than that of the WebRTC algorithm. In addition, the speech output of the proposed algorithm during the double-talk periods was clear and coherent.