# File lib/rubygame/sound.rb, line 346
  def fade_out( fade_time )
    if( fade_time < 0 )
      raise ArgumentError, "fade time cannot be negative (got %.2f)"%fade_time
    end

    if channel_active?
      SDL::Mixer.FadeOutChannel( @channel, (fade_time * 1000).to_i )
    end

    return self
  end