{'fraction_non_alphanumeric': 0.017085427135678392, 'fraction_numerical': 0.004020100502512563, 'mean_word_length': 5.384615384615385, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
A simplified structure of second-order volterra filters for nonlinear acoustic echo cancellation

The cascade connection of a 2nd order Volterra filter (VF) with a linear transversal filter is often used in nonlinear acoustic echo cancellation (AEC) to model a nonlinear echo path comprising a nonlinear loudspeaker and a linear room impulse response. This cascade-form AEC, however, often suffers from divergence, since its nonlinear and linear constituents are updated separately and a global convergence toward the minimum residual echo error is hardly guaranteed. In this paper, we propose a simplified 2nd order VF that is equivalent to the cascade structure for nonlinear AEC. The new structure has much fewer coefficients than the conventional direct-form 2nd order VF does, while enjoys a better convergence performance compared to both the cascade canceller and the conventional 2nd order VF. Computer simulation based experiments have confirmed the advantage of the proposed structure.