The audio properties is the second tab in the Properties panel. There are similar to the video properties. You can change the properties for an entire clip or for a specific time with an audio action as shown in the video properties and actions clip. With volume you can change the volume of the current clip, but we also have ducking with docking you can change the volume of the other clips while this clip is playing. You can use docking to lower the background music while you say something important. You can also mute the clip.

If the audio has very high or low volume, you can smooth the volume levels. You can combine the stereo into mono and also apply audio effects. To remove background noise use the background noise filter. Very useful when you want to remove back keyboard clicks. And you can also add an audio filter in the same way I've shown you individual actions clip