Penghapus Derau Adaptif dengan Algoritma NLMS Ukuran Langkah Adaptasi Tetap dan Berubah

Penghapus derau adaptif adalah penapis optimal yang dapat diterapkan bila masukan referensi tersedia. Keuntungan metode ini adalah kemampuan adaptasi dan distorsi keluaran yang rendah. Penggunaan ukuran langkah yang tepat memberikan kecepatan konvergensi yang tinggi. Penelitian ini memodifikasi ANC klasik sehingga memberikan kecepatan konvergensi yang lebih tinggi dan distorsi sinyal keluaran yang lebih rendah. Seratus iterasi pertama menerapkan ukuran langkah tetap kemudian berubah-ubah untuk iterasi berikutnya. Ukuran langkah modifikasi ini berdasar pada estimasi SNR. Simulasi komputer dengan derau putih, menunjukkan ANC usulan mempunyai distorsi 10 hingga 20 dB dibawah ANC klasik

Adaptivni sustav za poništavanje utjecaja šuma motora na mobilne komunikacije

An adaptive system, which provides engine noise cancellation for hands-free cellular phones is developed. The system employs a cascade of three second-order adaptive notch/bandpass filters based on Gray-Markel lattice structure. This structure defines the high stability of the adaptive system. A Newton type algorithm is used for updating the filter coefficients that determines fast adaptation. In addition a new algorithm using adaptive filtering with averaging (AFA) is developed. The main advantages of AFA algorithm could be summarized as follows: high convergence rate comparable to that of the recursive least squares (RLS) algorithm and at the same time low computational complexity. The presented adaptive system for engine noise cancellation could improve considerably the speech intelligibility of hands-free cellular phones.Razvijen je adaptivni sustav koji poništava utjecaj šuma motora pri korištenju mobitela bez uporabe ruku. Sustav koristi kaskadu koja se sastoji od tri adaptivna filtra drugog reda s karakteristikom pojasnog propusta ili pojasne brane zasnovana na Gray-Markel rešetkastoj strukturi. Ta struktura osigurava veliku stabilnost adaptivnog sustava. Za određivanje koeficijenata filtra primijenjen je algoritam Newtonovog tipa. Ovaj algoritam osigurava brzu adaptaciju. Dodatno je razvijen novi algoritam koji koristi adaptivno filtriranje s usrednjavanjem (AFA). Glavne su prednosti AFA algoritma velika brzina konvergencije usporediva s brzinom konvergencije rekurzivnog algoritma najmanjih kvadrata (RLS) te niska kompleksnost izračunavanja. Prikazani adaptivni sustav za poništavanje utjecaja šuma motora mogao bi značajno poboljšati razumljivost govora pri korištenju mobitela bez uporabe ruku

New Variable Step-Size NLMS Algorithm for Adaptive Noise Cancellation

Numerous Variable Step-Size Normalized Least Mean Square (VSS-NLMS) algorithms have been proposed to solve the problems of fast convergence rate and low value of steady-state misadjustment in the past three decades. In this paper we propose a new VSS-NLMS algorithm that employs the estimated power ratio of the adaptive filter to control the step-size update. The algorithm has a large step size in the initial stages to speed up the convergence rate, and then the step size is adjusted to maintain a low value of steady-state misadjustment. The performance of the proposed algorithm is evaluated for Adaptive Noise Canceller (ANC) using different speech signal with stationary and non-stationary noise added to it. The computer simulation highlights that the proposed algorithm has very fast convergence rate while maintaining a very low value of steady-state misadjustment