{'fraction_non_alphanumeric': 0.019569471624266144, 'fraction_numerical': 0.0, 'mean_word_length': 5.39375, '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}}
Estimation of time-variant acoustic feedback paths in in-car communication systems

In-car communication systems aim at improving the speech communication inside a vehicle by picking up the talking passenger's voice by means of microphones and playing it back over loudspeakers that are located close to the listening passengers. Because of this closed-loop operation, system instability caused by acoustical feedback is a limiting factor for the maximum possible system support. In this contribution, we present a feedback cancellation algorithm based on the NLMS algorithm for estimating the frequency responses of the multiple, time-variant feedback paths. The step-size parameter is calculated time- and frequency dependently and signal decorrelation, which is necessary for convergence of the filters, is performed by a phase modulation filter for frequency shifting. Measurements in a test car prove the effectiveness of the approach in the in-car communication application, even in the presence of background noise.