If you've already reached episode 2 in D4, then you've defenitely realized those boxes with "Desert" written on it. They appear about every hour and you'll get one of about 20 rare items, some time you don't get one but instead some food or drink.
Some of this rare items are those audio files (for example 9 & 10) and clothing for all of the characters as well as beards.

This guide will help you get all of those rare items in about 1h.

With this guide you will be able to almost farm those packages at the front door, in about 1h you should have gotten every piece of item that can be achieved trough those boxes.

- Start Steam in offline mode
- Enter the game and play episode 2 until you can dive
- (If there is already a box, open it)
- Dive into the story
- Tab out of the game and change your PC time, add 1h
- Go back to the game and go back to the apartment
- There should be a box now

Continue:
Dive > Time Change > Back > Box > Dive > ...

To change the time on your PC (Windows 10) do the following:

- Search for "Date and Time" at the Windows Search Option
- Disable automatic time settings
- Choose "Change" at "Date and Time"
- After every try add about 1 hour

If you're having trouble with changing your time (older/newer Versions), just google it!