Aliasing and SRC Examples Bob Smith, Principal Scientist Acoustic Systems, Physio-Control Overview Loose Visual Analogies to Audio Degradation Aliasing and A/V Demonstration Filter types step response SRC Examples Loose Visual Analogies Incremental Degradation Aliasing Tektronix Aliasing Demonstration A 2794 Hz tone (F7) with multiple harmonics will be varied over a range of to cents in pitch. The tone and its harmonics have been suppressed with a tracking filter enhancing audibility of the aliases. Note how the minor change in tone frequency produces large changes in the frequencies of the aliases. Filter types step response Linear Phase Minimum Phase Hybrid 1 Hybrid 2 SRC Examples [x, fs]=wavread('bzzzt48_96.wav'); xt=fft(x); clf(); xlabel('Frequency Hz'); ylabel('log magnitude'); lab=sprintf('Sampling rate is %d ',fs); title(lab); labf=fs/4 lab2=sprintf('%d',labf); lab3=sprintf('%d',2*labf); lab4=sprintf('%d',3*labf); lab5=sprintf('%d',4*labf); tickloc=rows(xt)/128 if (fs==88200) set (gca, 'xtick', [0 35*tickloc 64*tickloc 93*tickloc 128*tickloc]); else set (gca, 'xtick', [0 32*tickloc 64*tickloc 96*tickloc 128*tickloc]); endif set (gca, 'xticklabel', {'0', lab2, lab3, lab4, lab5}); hold on; semilogy(abs(xt)); hold off; SRC Demo CEP2 48 to 96 KHz Audacity 48 to 96 KHz NCH 48 to 96 KHz NCH 48 to 88 KHz