BEFORE I start this, I want to say that the current sound system is a good step in the right direction and the developers are doing a great job, however, I think the sound system could be improved upon.
Sounds should be muffled when you're not in the room they occur in. Example: If a player gets caught in the room above where another player is, the player above should be able to slightly hear the scream, but it shouldn't be entirely clear like it is right now. Sound occlusion is the proper term and it adds so much to the immersion of the game. It should also apply to voice chat.
https://www.youtube.com/watch?v=5R_32a3a0eM
This is a video that showcases the difference in sound occlusion and how it can contribute to a more realistic soundspace. I feel like this could really help with immersion and atmosphere of the game, and would be beneficial to help the game's horror vibe.
In this showcase, we've used Steam Audio plugin with Unity. Depending on the geometry and preferred settings, the audio source will behave differently compared to the native source. All in realtime, no baking required.
For more information: https://valvesoftware.github.io/steam-audio/