Oh, sorry about the sound jargon. Stingers can be environmental sounds, but typically they are very short tonal (that is, very short "music) elements that is played based on in-game triggers/cues. It's very typical for AA games to have it, but not mandatory if you have different game design concepts in mind.
Also, you could probably work on the reverb of the spoken dialogues. They way it is doesn't really sound its coming from a radio, that's because of acoustics! If you're interested in that I could further explain/help.
What's your current plans for game development?
Thank you for clarifying! My current plans are to do some minor improvements, and see how it turns out in the Godot jam. If it gets much reception I'll maybe make a bigger game out of it. After all it's still a smaller hobby project I am working on next to my Master of Computer Science and I can't spend full time on it. :)
Coolio! Looking forward in case you decide to take things further! By the way the plugin to simulate different acoustics (such as the sound coming from an actual phone or walkie-talkie), check "Place It" from Soundly. You can run the plugin in your DAW and apply the sound effects.
https://getsoundly.com/tools/