Adding comments to the speech_analysis

speech_analysis.m

@@ -1,30 +1,117 @@
+%loading the signal library in octave
 pkg load signal
 clear all
 close all
 
-[y,fs]=audioread('modulator22.wav');
+%reading of the orignial signal in data
+[y,fs]=audioread('./data/modulator22.wav');
 
+%calculation of the time from the sampling frequency
 t=0:1/fs:length(y)/fs-1/fs;
 
+%showing the original signal
 ##figure;
 ##set(gcf, 'name','Signal of origin');
 ##plot(t,y);
 ##xlabel('time(s)');
 ##ylabel('amplitude(n.u.');
 
+%save a speed down version of the original signal
+audiowrite('./data/modulator22_speedown.wav', y , fs/2);
 
-audiowrite('modulator22_speedown.wav', y , fs/2);
+%save the speed down version's signal and sampling frequency  and calculate it's new time duration
-[y_speedown,fs_speedown]=audioread('modulator22_speedown.wav');
+[y_speedown,fs_speedown]=audioread('./data/modulator22_speedown.wav');
 t_speedown=0:1/fs_speedown:length(y_speedown)/fs_speedown-1/fs_speedown;
 
+%showing the speed down version's signal
 ##figure;
 ##set(gcf, 'name','Speed down of the signal of origin');
 ##plot(t_speedown,y_speedown);
 ##xlabel('time(s)');
 ##ylabel('amplitude(n.u.');
 
+%Apply the DFT(flase) and FFT(true) to the speed down signal
 %frequencySpectrum(y_speedown, fs_speedown, false);
 %frequencySpectrum(y_speedown, fs_speedown, true);
 
+%Illustrate the spectogram of the speed down version at 2 windows values (1 for a precise frequency read and 1 for a precise time domain)
 %spectrogram(y_speedown, fs_speedown, 5, 30);
 %spectrogram(y_speedown, fs_speedown, 5, 5);
+
+%Lowering the sampling frequency using the downsample() function
+##y_downsampled = downsample(y, 2);
+##fs_downsample = fs/2;
+##audiowrite('./data/modulator22_downsample.wav', y_downsampled , fs_downsample);
+##t_downsample=0:1/fs_downsample:length(y_downsampled)/fs_downsample-1/fs_downsample;
+
+%Lowering again the sampling frequency but with the decimate() function (applying a LP filter at the start )
+##y_decimated = decimate(y, 2);
+##fs_decimate = fs/2;
+##audiowrite('./data/modulator22_decimate.wav', y_decimated , fs_decimate);
+##t_decimate=0:1/fs_decimate:length(y_decimated)/fs_decimate-1/fs_decimate;
+
+%Comparing them both on the same graph to see the effect of the LP filter on the signal itself
+##figure;
+##set(gcf, 'name','Decimate vs Downsample');
+##title('Decimate vs Downsample');
+##plot(t_downsample,y_downsampled,'b');
+##hold on;
+##plot(t_decimate,y_decimated,'g');
+##xlabel('time(s)');
+##ylabel('amplitude(n.u)');
+##legend('downsample()','decimate()',"location","southeastoutside");
+
+%Illustrating them with their frequencySpectrum to see the effect of the LP filter
+##frequencySpectrum(y_decimated, fs_decimate, true);
+##frequencySpectrum(y_downsampled, fs_downsample, true);
+
+%%%IIR and FIR LP FILTER IMPLEMENTATION %%%%
+%creating a low pass filter FIR 
+N=30;
+fc=1000;
+bfir=fir1(N,fc/(fs/2));
+freqz(bfir,1);
+
+%filter the signal
+y_FIR_filter=filter(bfir,1,y);
+
+%plot of the signal FIR
+##figure;
+##plot(y_FIR_filter,'g');
+
+%creating a low pass filter IIR
+N=8;
+fc=1000;
+[biir,a]=butter(N,fc/(fs/2));
+freqz(biir,a);
+Z=roots(biir); %zeros of the transfer fct
+P=roots(a); %poles fo the transfer fct
+
+%representation of zeros/poles in complex plan
+##figure;
+##zplane(Z,P);
+##title('Zeros and poles of the transfer function of the IIR filter');
+##legend('zeros','poles');
+##grid on;
+
+%filter the signal
+y_IIR_filter=filter(biir,a,y);
+
+%plot of the signal IIR
+##figure;
+##plot(y_IIR_filter,'b');
+
+%downsample of the IIR signal
+y_IIR_downsample = downsample(y_downsampled, 2);
+fs_IIR_downsample = fs/2;
+t_IIR_downsample=0:1/fs_IIR_downsample:length(y_IIR_downsample)/fs_IIR_downsample-1/fs_IIR_downsample;
+
+figure;
+set(gcf, 'name','Downsample of IIR');
+plot(t_IIR_downsample,y_IIR_downsample,'b');
+xlabel('time(s)');
+ylabel('amplitude(n.u)');
+legend('downsample()',"location","southeastoutside"); 
+
+
+