Most audiobooks are just somebody reading the book out loud. Oh they might change their voice once in a while or use a sound effect or two, but yeah...it's the digital equivalent of saying, "Dad, I want a bedtime story." I create audio dramas, and let me tell you, there have been moments when I had up to nine simultaneous sounds going...everything from random indoor noises to actors, sound effects, narration, and music. Part one of Harrod's Bend (Chapter 2) is like that. When a hot air balloon catches on fire, it's not just flames like a fireplace. It's a whoosh, a crackle, a crumble, and a sizzle. All the while the audience is going nuts, Ripley is making his escape, and the narrator is covering it blow by blow.
The next story is already in the can, a lush adaptation of "Swept Away," and one sword fight ends with the baddie getting skewered by a sword. I wanted you to experience it intensely, so I used a large knife and a watermelon.
The most eerie effect I know how to do is the "Angry God" voice from Star Trek V. You can find clips of the scene on Youtube if you don't want to invest in the movie. The voice seemed to resolve from anticipatory sound, an effect that gives you the impression of someone who is speaking to you but whose psychic energy is so powerful that you hear him thinking the words right before they leave. For your edification, record your voice. It helps if you use a very deep voice and speak slowly and clearly. Then REVERSE the track. Yes, I said esreveR the track. Only then do you add large room reverb to it. So you put reverb on your voice BACKWARDS, then you reverse it again and listen. That is astonishing enough, but then trim it out by giving this eerie track a forward SMALL ROOM reverb so the words don't snip off at the end. I freaked out my wife (LadyBadger) with a line from the movie. "You are the first of your kind to find me here. Your journey could not have been an easy one." She glanced at me and asked, "What did I marry???"