Audio is very important to the visual parts of media because it amplifies the emotion of whatever scene is playing. It helps the audience have more emotion to the visuals they are watching. A great example of this is in horror movies, often times the audience can sense when the movie is trying to scare them when the audio goes silent, signaling that a loud noise is going to follow to scare the audience. Having your visuals tie into your audio is what makes the effect, you need them to intertwine with each other. You need to put the audience into your visuals, and you do that by the audio, wherever your audio is would also be where your audience is.