Algoritmo para o Fator de Esquecimento do Método Cepstral de Cancelamento de Realimentação Acústica

Abstract

Resumo-Este trabalho propõe uma melhoria no método de cancelamento de realimentação acústica baseado no cepstro do sinal de erro. Essa melhoria consiste em um algoritmo para transformar o fator de esquecimento, parâmetro que controla o compromisso entre robustez a perturbações de curta duração e capacidade de rastreamento do filtro adaptativo, em variante no tempo. Simulações demonstraram que esse algoritmo faz o método apresentar um melhor compromisso entre velocidade de (re-)convergência e limite de desalinhamento, aumentando de modo geral a margem de estabilidade do sistema de sonorização. Palavras-Chave-Cancelamento de realimentação acústica, método cepstral, fator de esquecimento.

A Cepstral Method to Estimate the Stable Optimal Solution for Feedforward Occlusion Cancellation in Hearing Aids

“…It is clear that ( ) relies directly on ( ) and ( ) but is independent of ( ). The independence of ( ) is an important advantage over the open-loop cancellation structure proposed in [1]. Due to the properties of the DTFT, ( ) is absolutely summable and therefore this optimal solution is stable.…”

“…2) Acoustic path: The acoustic path is represented in two different ways. First, as done in [1], [12], the acoustic path is a delay line defined as…”

“…The adaptive method in [14], on the other hand, employs a feedback scheme. More recently, a fixed controller operating on a feedforward cancellation structure was proposed in [1].…”

“…Among the aforementioned cancellation proposals, the work presented in [1] stands out for being the only one to estimate the occlusion path, nomenclature for designating the system that models the bone conduction of the sound pressure produced by the laryngeal vocalizations to the blocked ear. The estimation is performed by assuming knowledge of the acoustic path, system that denotes the acoustic coupling between the user lips and the hearing aid external microphone.…”

“…As a possible answer for these limitations, [1] is expanded in this paper. The goal of this work is twofold: first and foremost, without assuming to know the acoustic path, to propose a cepstral method for estimating the stable optimal solution of the feedforward occlusion cancellation; second, to propose a controller designed based on this estimate and without assuming to know the forward path for attenuating the occlusion effect in the feedforward cancellation structure.…”