spkVocPlay()

         Plays a file with VOC format by the speaker

    Syntax:

         spkVocPlay( cFile [, nRate] ) -> lError

         cFile : The name of the VOC file
         nRate : The frequency ratio. Default value is 12000 Hz.
                 Use this value for frequency changes.

    Description:

         Plays a file with VOC format by the speaker.

    Return:

         A logic value indicating if the function finished without error

    Example:

         spkVocPlay( "Handel.voc", 13224 )