diff --git a/TP3a/DiogoEliseu_TP3_2.m b/TP3a/DiogoEliseu_TP3_2.m
index 477815b..93f07bc 100644
--- a/TP3a/DiogoEliseu_TP3_2.m
+++ b/TP3a/DiogoEliseu_TP3_2.m
@@ -31,7 +31,7 @@ figure(1)
 
 subplot(2,1,1)
 plot(sintetico);
-xlabel('t'), ylabel('sintetico(t)'), title('sinal sintetico');
+xlabel('t'), ylabel('sintetico[t]'), title('sinal sintetico');
 
 subplot(2,1,2)
 DFT_synth = fft(sintetico, Ls);
@@ -43,7 +43,7 @@ figure(2)
 
 subplot(2,1,1)
 plot(cello.x);
-xlabel('t'), ylabel('cello(t)'), title('sinal cello');
+xlabel('t'), ylabel('cello[t]'), title('sinal cello');
 
 subplot(2,1,2)
 DFT_cello = fft(cello.x, Lc);
@@ -55,7 +55,7 @@ figure(3)
 
 subplot(2,1,1)
 plot(EEG);
-xlabel('t'), ylabel('eeg(t)'), title('sinal EEG');
+xlabel('t'), ylabel('eeg[t]'), title('sinal EEG');
 
 subplot(2,1,2)
 DFT_EEG = fft(EEG, Le-1);
diff --git a/TP3a/DiogoEliseu_TP3_4.m b/TP3a/DiogoEliseu_TP3_4.m
new file mode 100644
index 0000000..465044d
--- /dev/null
+++ b/TP3a/DiogoEliseu_TP3_4.m
@@ -0,0 +1,40 @@
+%% Inicialização do ambiente
+clear ; close all; clc
+
+%% Exercício 4
+fc = 0.3;
+w = linspace(0, pi, 500); %0:pi/500:pi;
+f = w/pi;
+order = [ 4, 6, 8, 10];
+
+for i=1:4
+    % Butterworth
+    subplot(3,4,i)
+    [num, den] = butter(order(i), fc, 'low'); %order, cutoff frequency, type
+    h = freqz(num, den, w);
+    gain = 20.*log10(abs(h));
+    plot(f, gain);
+    axis([0 1 -60 2]);
+    title(['Butterworth - ' num2str(order(i)) '.ª Ordem']);
+    ylabel("Ganho (dB)"); xlabel("\omega/\pi");
+    
+    % Chebyshev
+    subplot(3,4,i+4)
+    [num, den] = cheby1(order(i), 0.5, fc, 'low'); %0.5 is tollerance in dB
+    h = freqz(num, den, w);
+    gain = 20.*log10(abs(h));
+    plot(f, gain);
+    axis([0 1 -60 2]);
+    title(['Chebyshev - ' num2str(order(i)) '.ª Ordem']);
+    ylabel("Ganho (dB)"); xlabel("\omega/\pi");
+    
+    % Eliptico
+    subplot(3,4,i+4+4)
+    [num, den] = ellip(order(i), 0.5, 40, fc, 'low'); %0.5 is the tollerance in the top, -40 is the tollerance in the bottom
+    h = freqz(num, den, w);
+    gain = 20.*log10(abs(h));
+    plot(f, gain);
+    axis([0 1 -60 2]);
+    title(['Eliptico - ' num2str(order(i)) '.ª Ordem']);
+    ylabel("Ganho (dB)"); xlabel("\omega/\pi");
+end