Realiojo laiko aido malšinimo sistemos projektavimas ir tyrimas

Abstract

Baigiamajame magistro darbe projektuojama ir tiriama realiojo laiko aido malšinimo sistema. Darbe išanalizuoti akustinį aidą sukeliantys veiksniai ir akustinio aido sukeliamos problemos. Išnagrinėti netiesinio aido malšinimo būdai ir algoritmai. Atlikus analizę nuspręsta naudoti adaptyvųjį filtrą, kuris paremtas normuoto mažiausio vidutinio kvadrato algoritmu. Filtro koeficientams atnaujinti pasirinktas normalizuotas abipusės koreliacijos algoritmas, kuris atlieka dvigubos kalbos detektoriaus funkciją. Taip pat liekamajam aidui malšinti naudojamas netiesinis procesorius. Atlikus analizę sudarytas akustinio aido malšinimo sistemos algoritmas „Matlab“ programavimo kalba. Šis algoritmas taip pat ištestuotas „Matlab“ aplinkoje. Patvirtinus algoritmo veikimą, jis perrašytas C programavimo kalba. Algoritmui testuoti suprojektuota principinė elektrinė schema ir jos spausdintinė plokštė. Spausdintinė plokštė sulituota ir ištestuota. Akustinio aido malšinimo algoritmas ištestuotas realiuoju laiku, malšinimas pasiektas didesnis nei 30 dB. Darbo apimtis – 76 p. teksto be priedų, 43 iliustr., 18 lent., 24 bibliografiniai šaltiniai. Atskirai pridedami darbo priedai.

In the final master's thesis real-time echo cancellation system is designed and investigated. Factors causing acoustic echo and problems caused by acoustic echo was analyzed. The methods and algorithms for nonlinear echo cancellation were examined. After the analysis, it was decided to use an adaptive filter based on the normalized least mean square algorithm. A normalized cross correlation algorithm has been selected for updating the filter coefficients, which performs the function of a double talk detector. Also a non-linear processor was used to suppress residual echo. After analysis, the acoustic echo cancellation algorithm was developed in “Matlab“ programming language. This algorithm was also tested in the “Matlab“ environment. After verifying the operation of the algorithm, it was rewritten in C programming language. Electrical scheme and its printed circuit board was designed for algorithm testing. Printed board was assembled and tensed. The acoustic echo cancellation algorithm was tested in real time and the echo cancellation is greater than 30 dB. Thesis consist of: 76 p. text without appendixes, 43 pictures, 18 tables, 24 bibliographical entries. Appendixes are attached separately.