Fs = 44100;
t = 0:1/Fs:1-1/Fs;
M3AnO = cos(2*pi*1000*t)+randn(size(t));
M3A = cos(2*pi*500*t)+filter(1,-0.9,rand(size(t)));
[Pxx1,Fxx] = periodogram(M3AnO,[],length(M3AnO),Fs);
[Pxx2,Fxx] = periodogram(M3A,[],length(M3A),Fs);
plot(Fxx,10*log10(Pxx1)); hold on;
plot(Fxx,10*log10(Pxx2),'r'); hold on;
set(gca,'xlim',[0 2000]);
legend('M3AnO','M3A','Location','NorthEast');
xlabel('Hz'); ylabel('dB/Hz');
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