Design and analysis of a BLPC vocoder-based adaptive feedback cancellation with probe noise

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• 作者：Ankita Anand^a ; ^{saiankitaanand@gmail.com" class="auth_mail" title="E-mail the corresponding author} ; Asutosh Kar^b ; ^{asuka@es.aau.dk" class="auth_mail" title="E-mail the corresponding author} ; M.N.S. Swamy^c ; ^{swamy@ece.concordia.ca" class="auth_mail" title="E-mail the corresponding author}
• 关键词：Adaptive filters ; Feedback cancellation ; Probe noise ; Hearing-aid ; Band-limited LPC vocoder ; Misalignment
• 刊名：Applied Acoustics
• 出版年：2017
• 出版时间：1 January 2017
• 年：2017
• 卷：115
• 期：Complete
• 页码：196-208
• 全文大小：2357 K

文摘

The band-limited linear predictive coding (BLPC) vocoder-based adaptive feedback cancellation (AFC) removes the high-frequency bias, while the low frequency bias persists between the desired input signal and the loudspeaker signal in the estimate of the feedback path. In this paper, we present a BLPC vocoder-based adaptive feedback canceller with probe noise with an objective of reducing the low-frequency bias in digital hearing-aids. A step-wise mathematical analysis of the proposed feedback canceller is presented employing the recursive least square and normalized least mean square adaptive algorithms. It is observed that the optimal solution of the feedback path is unbiased for an unshaped probe noise, but is biased for a shaped probe signal; the bias term does not consist of correlation between the desired input and the loudspeaker output. The identifiability conditions are analysed and it is shown that a delay, greater than or equal to the length of the adaptive filter, must be introduced in the forward path to achieve an unbiased feedback path estimate. Algorithm analysis and computer simulations presented in this paper justify the reason for selecting the proposed design over the existing BLPC vocoder-based feedback cancellation algorithm.