# ceciliacasarini/Aliasing

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 close all clc %~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~% % ALIASING MOZART % % Author: Cecilia Casarini % %~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % In this script the concept of aliasing is illustrated by modifying the % sample rate in a famous aria from Mozart: Der Hölle Rache. To obtain the % effect we just discard some samples, e.g. we keep one every two samples % to halve the sample rate, then 1 over 4 and so on. %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % Reading the .wav file [y, fs] = audioread('Mozart_derhollerache_Fs_44100Hz.wav'); % Using just one channel y = y(:,1); % 1. Sampling at half the sample rate y1 = y(1:2:end); % Normalizing the signal y1 = y1./max(abs(y1(:))); % Sample rate fs1 = round(fs/2); % Play soundsc(y1, fs1); pause % 2. Sampling at 1/4th of the sample rate y2 = y(1:4:end); % Normalizing the signal y2 = y2./max(abs(y2(:))); % Sample rate fs2 = round(fs/4); % Play soundsc(y2, fs2); pause % 3. Sampling at 1/8th of the sample rate y3 = y(1:8:end); % Normalizing the signal y3 = y3./max(abs(y3(:))); % Sample rate fs3 = round(fs/8); % Play soundsc(y3, fs3); pause % 4. Sampling at 1/16th of the sample rate y4 = y(1:16:end); % Normalizing the signal y4 = y4./max(abs(y4(:))); % Sample rate fs4 = round(fs/16); % Play soundsc(y4, fs4); % Saving .wav files % audiowrite('Mozart_derhollerache_Fs_22050Hz.wav', y1,(fs1)); % audiowrite('Mozart_derhollerache_Fs_11025Hz.wav', y2,(fs2)); % audiowrite('Mozart_derhollerache_Fs_5513Hz.wav', y3,(fs3)); % audiowrite('Mozart_derhollerache_Fs_2756Hz.wav', y4,(fs4));