Question

Explain the filtering of the human speech signal. How can we filter the noisy speech signal from the other sound sources which have high frequency components. Write a matlab script to filter this noisy speech signal from the noise. . The cutoff frequeny of the filter is 3000hz?

Answer 1

clc;
clear all;
close all;
%% time domain
t = 0:1/1024:1;
x = sin(2*pi*50*t);

a = 5;
b = 2;

p = length(t);
e = rand(1,p);
n = (-1/a)*(log(1-e));

ns=x+n;

subplot(2,2,1);plot(t,ns);

[b,a] = butter(8,0.2,'low');
y = filter(b,a,ns);
subplot(2,2,2);plot(t,y);

  
%% freq domain
t1 = 0:2/1024:1-2/1024;
X=abs(fft(x));
subplot(2,2,3);
for i=2:6:18
[b,a] = butter(i,0.2,'low');
y = filter(b,a,ns);
F = abs(freqz(b,a,floor(length(ns)/2)));
temp=X(1:floor(length(X)/2));
temp=temp/max(temp);
plot(t1,temp);
hold on
plot(t1,F);hold on
end

%In the above program i in for loop indicates order of the filter and 0.2 and 0.8 indicates normalized frequency where you %need to consider one sampling frequency, so this program gives the fft output if you want convert to time domain by using %command ifft of the X and verify. y is the filtered output signal