title: Matlab 30 Khz still be heard
body: <p>By using the Matlab code as below, I created 30 Khz signal and used sound function to hear the signal created. But, according to my knowledge, I, as a human, should not have heard anything above 20Khz. What is the part that i am missing below? Am I not a human? </p>
  
  <pre><code>clear
  Fs = 96000;
  toneFreq1 = 30000;   
  nSeconds = 2;
  f1 = 10*cos( linspace (0, nSeconds*toneFreq1*2*pi, round(nSeconds*Fs) ) );
  freqz( f1, length(f1) )
  sound(f1, Fs); 
  </code></pre>