Stop the Violins!


Background Process Group Images Code

Code



 
 
 
Process.m
    function [out] = process(in,key)
    %PROCESS takes in a sound vector and a vector containing the %target signal
    %and outputs a filtered version of the original signal
    a = in;
    b = a(:,1);                           %take only the first channel
    l = length(b);                        %length of the input signal
    n = floor(l/1024);                    %number of fourier transforms
    out = zeros(n*1024,1);                %output vector to be filled
    for c = 0:n-1
     r = b(1024*c+1:1024*(c+1));          %sampling the signal
     d = fft(r,1024);                     %putting the sample into f-domain
     e = stopbands(d,key);                %this is a filtered signal
     f = ifft(e,1024);                    %returning the sample to time domain
    out(1024*c+1:1024*(c+1)) = f;         %reconstituting the vector of samples
    end
    out = 5.*out;                         %this amplifies the signal
 

Findvoice.m
    function [index] = findvoice(spec,key)
    %FINDVOICE takes in a spectrum and a frequency pattern and returns the integer
    %showing how many indices the pattern was shifted in order to correlate maximally with
    %the input signal
    specl = spec;                         %artifact
    corr = xcorr(key,specl);             %finding the correlation between signals
    index = 1;
    M = max(corr);
    while corr(index)~=M                 %finding the index of maximal correlation
    index = index+1;
    end
    ls = length(spec);
    lk = length(key);
    if ls>lk                             %finding the actual shift
     l = ls;
    else
     l = lk;
    end
    index = index-l;                     %amount that the pattern was shifted
 

Stopband.m
    function [signal] = stopbands(vec,key)
    %STOPBANDS takes in a signal and a pattern and uses a matched filter to adaptively filter
    %the signal with two butterworth stopbands and an elliptical lowpass filter
    index = findvoice(vec,key);          %determining filter shift
    if abs(index)>50                     %sanity check on filter shift
    index = 0;
    else index = index;
    end
    fs = 44100;
    denom = fs/2;                        %normalizes cutoff freq.s
    factor = 43;                         %Hz per index of spectrogram
    W1 = (93+index)*factor/denom;          %lower limit
    W2 = (105+index)*factor/denom;       %upper limit
    Wstop = [W1 W2];                     %first stopband f-vector
    [stop1,stop2] = butter(3,Wstop,'stop','s');  %designing first stopband
    W3 = (162+index)*factor/denom;       %lower limit
    Wstop2 = [W3 W4];                    %second stopband f-vector
    [stop3,stop4] = butter(3,Wstop2,'stop','s');  %designing second stopband
    %Wlow = (139+index)*factor/denom;      %determining lowpass cutoff
    [low1,low2] = ellip(6,0.5,20,Wlow);    %designing the lowpass
    lowered = filter(low1,low2,vec);       %lowpass filter
    stopped = filter(stop1,stop2,lowered); %first stopband filter
    stopped = filter(stop3,stop4,stopped); %second stopband filter
    signal = stopped;

 
 
 
 

 
Background Process Group Images Code