Similar to a master bus or mix bus, your composition's audio properties are the final step before your Descript audio goes to your speakers or headphones. Your composition audio properties will affect the volume and panning, and apply audio effects to your entire composition's audio.
Access your composition's audio properties
Click on your composition's title at the top of the Script editor, and then the Layer section on the right-hand side. This will allow you to access the composition's audio properties. You can then make volume adjustments or add effects from the Layer panel.