Sound quality is the primary indicator of professionalism in videography.
The thing that is more noticeable than poor lighting or sloppy camera work is noisy sound. This is because bad sound really distracts the viewer from getting the message you are trying to relate with your video. I believe that you could possibly have great success communicating without any picture, if the audio is great (like radio) but a video with lousy sound is just annoying and amateurish. Of course there are exceptions and sometimes professionals intentionally distort audio to make it seem less polished for effect but, most of the time sound people are working toward making pristine audio recordings or (unfortunately) attempting to repair or salvage faulty audio tracks.