Any vibrations in a gas, a fluid (a gas is a kind of fluid), or a solid, if they are somewhere
between 20Hz and 15,000Hz, and if strong enough in amplitude, can be detected (sensed) by the hearing apparatus of most people. But categorizing a sound and deriving meaning from a sound is a completely different process from merely knowing a sound is happening. We categorize and interpret sounds by comparing them to other sounds we’ve heard, and how we and others responded to those sounds in the past.

To interpret a sound as speech, an animal call, music, thunder, etc., our brains rely heavily on comparison to sounds previously experienced. Though it’s true that certain kinds of sound dynamics: a sudden, “startling” sound for example, can have an emotional effect on us even if we have no idea what the sound is, that’s a pretty low bar in terms of the potential storytelling power that film directors depend on. You can “jump-scare” me easily and cheaply, and that can be fun, but that’s not going to bring me into the story in the ways that sounds I can relate to and already have feelings about can.

Newborn infants can be jump-scared with sound, and they are more likely to be soothed by harmony than by dissonance, but once again that’s a very low bar. Experiments have shown that infants don’t respond any more positively to intricate harmonies than they do to a steady set of two tones that are harmonious rather than dissonant.

There’s a strong myth that some of the most emotionally powerful sounds in film history were unlike anything previously heard. Did you know that voice of the Wookie in Star Wars is a bear? And not even an exotic kind of bear, just a normal black bear that most of us have heard since childhood in nature documentaries and in zoos. The main element of the T-Rex voice in Jurassic Park is an elephant, barely manipulated at all.

But part of movie magic, when it really gets to us, is that we are easily “hypnotized” by it, and we go into a state where we stop being analytical. If somebody plays a recording for us of a black bear vocalizing, most of us would guess what it is if we heard enough of it. But the fact that this reasonably familiar sound seems to be coming out of this very exotic-looking Wookie creature somehow shuts off the part of our brain that would normally and consciously compute “bear.”

It's extremely difficult for most directors, when they are watching scenes from their own movies, to stop being analytical and simply fall into the dream of the film. So their “bear detector” or “elephant detector” tends to be on constantly. They forget that the audience,
caught up in the story, is very unlikely to know or care in that moment exactly what they are hearing as long as it makes “emotional sense.”

So, directors, please don’t ask me to create a completely unique sound, one like nobody has ever heard. Even if I could produce one, and I don’t think anyone ever has, it would be very close to meaningless, and completely non-evocative to your audience.

You don’t want that.