title: Matlab Buttord returning Wn > 1 why?
body: <p>I am new to matlab and signals course, but i have a homework stating that I have to design a DT filter for Butterworth.
  I have these given parameters:</p>
  
  <ul>
  <li>The noisy signal is stored in the variable noisy and was sampled at
  44100 (fs) Hz. 
  <ol>
  <li>Passband edge: 2500 Hz.</li>
  <li>Stopband edge: 4000 Hz.</li>
  <li>Maximum gain in the passband Gpbmax: 40 dB.</li>
  <li>Minimum gain in the passband Gpbmin: 37 dB.</li>
  <li>Maximum gain in the stopband Gsbmax: −55 dB.</li>
  </ol></li>
  </ul>
  
  <p>What I did:</p>
  
  <pre><code>[n, Wn] = buttord(2500*2*pi, 4000*2*pi, 3, 55, 's'); 
  % Wn here is 1.5989e+04, I couldn't execute this without the 's' option.
  
  [b, a] = butter(n, Wn)
  The cutoff frequencies must be within the interval of (0,1).
  </code></pre>
  
  <p>Any answer please ?</p>