根據高階相關特性之非線性回音壓抑器

Abstract

為了去補償在免持聽筒或是視訊會議系統中所發生喇叭的非線性回音，通常使用非線性音訊回音消除器去消除此回音。不過這些方式的收斂速度太慢而影響效能。使用非線性回音壓抑方式即改善此問題。這是因為使用非線性回音壓抑時，不去找出實際的非線性路徑的部分。而是去找出非線性部份的能量頻譜密度。 這篇論文中，介紹兩種估計非線性回音能量頻譜密度的方式。第一種是以回音的相關性去估計出。第二種是使用非線性適應性濾波器去得到。然而使用第一種，會產生較大的誤差，是由於高階與一階回音不會是線性的關係。而第二種，需要大量的非線性濾波器去估計出高階的回音。在此篇論文將提出新的演算法，使用非線性適應濾波器去準確找出低階部分的回音，並且使用回音的相關性粗略估出高階部分的回音。此演算法能以少量的運算量較準確的估計出非線性回音的能量。另外對基底選擇提出分析方式，進一步的提升估計非線性回音的準確度。

In order to compensate the nonlinear distortion in the hands -free telephones or teleconferencing system, the nonlinear acoustic echo cancellation can be used to cancel nonlinear acoustic echo. However, the convergence speed of these methods is too slow. Nonlinear Acoustic Echo Suppressions will resolve the question. This is because we are not interested in an exact identification of the nonlinear components of the echo path. We are rather aiming at estimates power spectral density of the nonlinear components. In the thesis, two previous methods are introduced to estimate power spectral density of nonlinear residual error. First, use the linear property of echoes to estimate. Second, a nonlinear adaptive filter is used. We proposal the new method that can estimate low order echoes accurately and high order echoes roughly by less computational complexity than second method and estimate the nonlinear residual error more accurately than first method. And, we discuss how to choose echo basis.