You can make such adjustment to audio part as reducing noise or emphasizing human voice.
1) In the folder view of the [Effect] palette, click [AudioFilters] and display the filters.
Check the filter details in the description in the property, or by trying to apply the filter.
2) Drag and drop the filter to use to the clip on the timeline.
Alternative
Select a clip on the timeline. Select an effect in the [Effect] palette, and click [Add to Timeline].
Select a clip on the timeline. Right-click an effect in the [Effect] palette, and click [Add to Timeline].
Select an effect in the [Effect] palette, and right-drag it to the clip on the timeline, and click [Add] or [Replace].
