diff --git a/src/wav/question_3_3.m b/src/wav/question_3_3.m
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+% Charger les données
+load("signal_excitation.mat");  % xe1, xe2, fe sont chargés
+
+% Autocorrélation (centrée)
+rxe1 = xcorr(xe1, 'biased');
+rxe2 = xcorr(xe2, 'biased');
+
+% Axe des lags
+lags1 = -length(xe1)+1:length(xe1)-1;
+lags2 = -length(xe2)+1:length(xe2)-1;
+
+% Affichage
+subplot(2,1,1);
+plot(lags1, rxe1);
+title('Autocorrélation de xe1');
+xlabel('Décalage');
+ylabel('Amplitude');
+
+subplot(2,1,2);
+plot(lags2, rxe2);
+title('Autocorrélation de xe2');
+xlabel('Décalage');
+ylabel('Amplitude');
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