title: FileNotFoundError: [Errno 2] No such file or directory: 'ffprobe': 'ffprobe'
body: <p>When running the code snippet, I get the error seen in the title. </p>
  
  <p>I have re-installed the package <code>pydub</code>,and <code>pip3 install ffprobe</code>.</p>
  
  <pre class="lang-py prettyprint-override"><code>    from pydub.playback import play
      from pydub import AudioSegment
  
  
      def change_volume(file_name, alteration):
  
          song = AudioSegment.from_mp3(file_name)
  
          new_song = song + alteration
  
          new_title = ("_%s") % (file_name)
  
          new_song.export(new_title, format='mp3')
  
      change_volume("test_sample.mp3", 3)
  </code></pre>
  
  <p>The output of the code should be a new mp3 file in the directory with slightly risen volume levels (<code>test.mp3</code> --> <code>_test.mp3</code>), instead I get the error:</p>
  
  <pre class="lang-py prettyprint-override"><code>FileNotFoundError: [Errno 2] No such file or directory: 'ffprobe': 'ffprobe'
  </code></pre>