ANALYZING DIGITAL LOW PASS FILTERS

 % SURAJ BASTOLA %%%%%%%%%%%%

%%% Low Pass Filter %%%%%%%%%%

% IN MATLAB, Fs takes default value of 8000 %%%%%%%%%%%

clc;

clear all;

close all;

[y,Fs] = audioread('C:\Users\suraj\OneDrive\Documents\MIT COLLEGE\Software Defined Radio Communication\MATLAB COding\audioRecorded.wav');

z = abs(fft(y)); 

disp(z);

figure(1)

subplot(2,3,1)

plot(y)

title('Original Recorded Audio')

t = (0:length(y)-1)/Fs;

% ================ Low pass filter  using Chebyshev Window==============

% I have used 34th order FIR low pass filter 

% which has cut-off frequency0.48 and Chebyshev window with 30dB of ripple

blo = fir1(34,0.48,chebwin(35,30));

outlo = filter(blo,1,y);

ys = ylim;

subplot(2,3,2)

plot(t,outlo)

title('Lowpass Filtered Signal')

xlabel('Time (s)')

ylim(ys)

% ================ Low pass filter using Hamming Window==============

ord = 46;

low = 0.4;

bnd = [0.6 0.9];

bM = fir1(ord, [low bnd]);

Hamming = filter(bM,1,y);

subplot(2,3,3)

plot(t, Hamming)

title('Hamming window')

%=================== Low pass filter using Hamming Window==========

hM = fir1(ord,[low bnd],'DC-0',hann(ord+1));

Hanning = filter(hM,1,y);

subplot(2,3,4)

plot(t, Hanning)

title('Hanning window')

hfvt = fvtool(blo,1,bM,1,hM,1);

hfvt = fvtool(outlo,1,Hamming,1,Hanning,1);

legend(hfvt,'Chebwin','Hamming','Hanning')