When I work on a project I always add two markers. One little before the first sound in the project and one after the last sound has died out. Before I export Audio I "Select All" in the project and then position the cursor on the first marker and select "From now" and go to the last marker and select "Through now". it would make this process quicker if there was a button in the Audio Export window that does just that for me. Selects everything in the project between the first and last marker.
I have the computer in a diffrent room with screen and usb cables going through the wall. To get rid of irritating high frquency noice from the monitors I had to plug them into non-grounded power socket as they do not have Ground-lift button. Now I have very silent environment.