window and formant to find vowel

FT_times.m

@@ -16,4 +16,6 @@ for j = 1:item_num
 endfor
 
 printf('Average DFT time: %d \n', mean(times(1:item_num, 1)))
+printf('Standard deviation of DFT time: %d \n', std(times(1:item_num, 1)))
 printf('Average FFT time: %d \n', mean(times(1:item_num, 2)))
+printf('Standard deviation of FFT time: %d \n', std(times(1:item_num, 2)))

spectral_analysis.m

@@ -3,7 +3,44 @@ close all
 clc
 
 [y, fs] = audioread("sound/modulator22.wav");
-%frequencySpectrum(y, fs, 0); %true does FFT, false DFT
+ranges = [17000, 20000; 29000, 37000; 41000, 46000];
-step_size = 5; %ms
+one = y(ranges(1,1):ranges(1,2));
-window_size = 30;%ms
+two = y(ranges(2,1):ranges(2,2));
-spectrogram(y, fs, step_size, window_size)
+three = y(ranges(3,1):ranges(3,2));
+
+word = one;
+
+n = length(word);   
+f = (0:n-1)*(fs/n);
+f1 = 0;%Hz
+f2 = 4000;%Hz
+idx = find(f >= f1 & f <= f2); %define the index of the freq range
+f = f(idx);
+y = fft(word, n);% compute DFT of input signal
+power = abs(y).^2/n;
+power = power(idx);
+[val, ind] = max(power);
+
+%lowpass for the formant
+
+Fc = 2000; % define the cutoff frequency of the low-pass filter
+[b, a] = butter(6, Fc/(fs/2), 'low'); % design a 4th-order Butterworth low-pass filter
+Pxx_filt = filter(b, a, power); % apply the filter to the power spectrum
+length(Pxx_filt)
+length(f)
+
+
+figure;
+
+subplot(1,2,1) % time plot 
+plot(0:1/fs:(length(word)-1)/fs,word);
+xlabel('Time (s)');
+ylabel('Amplitude (a.u.)');
+
+subplot(1,2,2) % freq range plot 
+plot(f,10*log10(power/power(ind))); hold on;
+plot(f, 10*log10(Pxx_filt), 'r');
+xlabel('Frequency (Hz)')
+ylabel('Power (dB)')
+
+

spectrogram_analysis.m

@@ -0,0 +1,8 @@
+clear all
+close all
+clc
+
+[y, fs] = audioread("sound/modulator22.wav");
+step_size = 5; %ms
+window_size = 30;%ms, ideal value 25
+spectrogram(y, fs, step_size, window_size)