title: Methods to do outlier detection in sound recognition?
body: <p>There are models to recognize 2-class sounds, which are class-A and class-B.</p>
  
  <p>How to recognize class-C sounds as abnormal sound ?</p>
  
  <p>I tried to set a threshold while recognizing by frames.</p>
  
  <pre><code>above 70% -&gt; class A or B
  else      -&gt; abnormal
  </code></pre>
  
  <p>For example,</p>
  
  <p>If a sound has 10 frames, and the result is</p>
  
  <pre><code>frame 1 2 3 4 5 6 7 8 9 10
        A B A B A A A B A  A     A=7 B=3
  -&gt; class A
  
  frame 1 2 3 4 5 6 7 8 9 10
        B B A B A A A B A  A     A=6 B=4
  -&gt; abnormal
  </code></pre>
  
  <p>The performance is very bad.</p>
  
  <p>what should I do ?</p>