How to match indoor audio to outdoor clip

After Effects lacks the audio tools you need to clean up anything beyond a very basic audio mix. It is an effects and animation tool.

If you cannot record a simple background noise clip, lay it over both tracks and do a little simple mixing, try using the more advanced audio tools in Premiere Pro or Adobe Audition.

Premiere Pro and Audition contain many powerful tools for equalizing, removing background noise, and cleaning up audio tracks. The latest versions also have some good AI-supported tools to speed up the process and level out the recording. If that is not enough to fix your audio problems, you will have to add more tracks.

When I am filming actors or even shooting interviews, I will often record several seconds of Room Tone, Wild Sound, Ambient Noise, or Buzz Tracks that can be looped and added to the final mix to level out the audio. I have also collected a fairly large library of Wild Sound and different room tones (the sound in a room or hall when no one is talking), which I can add to an edit to help balance out the recording. Those sound effects are as important as the music in any feature film, documentary, or other film or audio recording to raise the production value to match what your brain does when you are talking and listening to the world around you. 

I hope this helps.