朱楠群(Nan-Chun Chu


基本資料


  
台北市

   
國立新莊高中
私立中原大學應用數學系
國立台灣科技大學資訊工程所

   
音樂,籃球,游泳,電影



論文研究

l           指導教授:古鴻炎老師

l           中文題目用於網路電話之雜訊刪減與迴音消除之研究

l           英文題目Noise Reduction and Acoustic Echo Cancellation for Voice over IP

l           中文摘要本論文研究製作迴音消除器與噪音刪減器軟體,然後放入WinRTP網路電話軟體裡,以提升網路電話的通話品質。在噪音刪減方面,先改進亂度偵測法來作語音活動偵測及估計雜訊頻譜,再研究以非線性頻譜刪減法和改良式頻譜刪減法,進行兩段式的頻譜刪減動作,來削減雜訊訊號。在迴音消除方面,採用正規化最小均方演算法製作一適應性濾波器,用以濾除迴音訊號,並且藉由分析電腦處理網路封包所導入之延遲時間,來降低適應性濾波器的計算量與加快收斂速度。依據實驗量測到的訊噪比與主觀聽測的評估分數,顯示我們的雜訊刪減器和迴音消除器的確可讓噪音訊號與迴音訊號都大幅的衰減,而使通話語音之品質獲得明顯的提升。

l           英文摘要In this thesis, we study the problems of acoustic echo cancellation and noise reduction, and develop the corresponding software modules. Then these modules are integrated into WinRTP internet telephony software package inorder to improve the quality of voice communication over IP network. For noise reduction, we first study to improve the entropy-based method for voice activity detection (VAD). According to VAD results, noise spectrum can be estimated. Thereafter, two modules of non-linear spectrum subtraction and improved spectrum subtraction are connected in two stages to reduce the noise more effectively. For echo cancellation, we use normalized-least-mean-square (NLMS) algorithm to build an adaptive filter to cancel echo signals.In addition, by analyzing and making use of the delay induced by computer processing of network packet, the convergence of the adaptive filter become more fast. Based on the signal-to-noise ration measured and the score obtained from subjective perception test voice guality, the noise subtraction and echo cancellation modules implemented here can indeed substantially attenuate the noise and echo signals. Therefore, the quality of communication voice is apparently increased.