SFX (short for sound effects) enhances the audio experience of videos and movies. If you want to improve your video projects, let me teach you what SFX is and how to use it effectively.
It might be tempting to assume that video is an entirely visual medium, where sound is an optional add-on, something nice to have but hardly essential.
In reality, any good film is built on its sounds.
If you look at this article’s cover image, you’ll probably imagine a gritty explosion sound effect, even though you can’t hear it. But you’ve heard it hundreds of times in movie scenes resembling the one pictured on the cover.
Great visuals without audio to accompany them will always be limited in their impact, especially if your goal is evoking emotion in your audience.
After all, humans aren’t only visual creatures.
At its core, filmmaking is all about storytelling. As you tell your story to the audience, you try your best to convince them that your story is true and that they should care about its characters.
The audience chooses to suspend their disbelief to gain the most entertainment from your movie.
The more detail and depth your film has, the more real it feels – and the more the audience will enjoy it.
Our world is filled with sound. Any world you build within your film will therefore feel hollow unless it’s also populated with noise of all kinds.
When you create a complex soundscape for your film, you encapsulate your audience in its world. And when they are encased, they feel like what they’re watching is real and become invested as a result!
If you’re still unsure that sound is the soul of filmmaking, let us convince you. In this article, we’ll cover exactly how SFX can elevate your art, as well as:
- What SFX is
- The different types of SFX
- Diegetic vs non diegetic sound
- Why sound matters
- A few iconic case studies and their use of sound.
Let’s dive right in!
What is SFX?
There’s some confusion around the term SFX, which is very understandable.
In filmmaking, there are two different accepted uses of the term SFX. It can stand for both Special Effects and Sound Effects.
Today, we’re talking about the latter (though the world of special effects is no less interesting).
Sound Effects in Film
A film contains countless sounds, everything from dramatic music and hushed whispers to the smash of a plate against a wall.
Generally, a film’s sound is divided into three main categories: dialogue, music, and sound effects.
The first two are obvious, but sound effects is a much more nebulous, wide-reaching category that can be a bit confusing at first – comprising anything that doesn’t fit into the first two types.
Dialogue and SFX
It’s easy to assume that dialogue and music will always be more important than SFX. After all, that’s where all the story and emotion is!
In reality, both of these are hollow without SFX. Sound effects are what create a world around your characters – one which breathes and whispers with all the believability of our own.
Used well, sound effects can evoke just as much intense emotion as music or dialogue.
Types of SFX
There are many sound effect categories; way too many to cover here reasonably.
For now, I will cover some of the most important categories from my experience as a sound designer and video creator. Remember that these aren’t always exclusive to one another; a sound effect may fall within several of these types simultaneously.
Diegetic vs Non-Diegetic Sound
All sound effects in a movie will be either diegetic or non-diegetic sounds. You may have seen the word diegetic thrown around if you’ve ever read or watched a film essay.
It’s a common term but one that is often misunderstood.
It originates from the Greek word diegesis, meaning narration. Initially, it was about oral storytelling, where the narrator built the whole world of the story with their words.
Over time, it’s come to mean something else in film, where we refer to the world of video as the diegesis. Therefore, if a sound is diegetic, it belongs to the world of the film.
To put it more simply: if the characters within the world could hear the sound, it’s diegetic. For instance, this could be a ringing phone, a shouting crowd, or screeching tires.
If it’s non-diegetic, then it’s only heard by the audience. This could be the dramatic strings of a jumpscare, overlayed narration, or a sitcom laugh track.
Music can be both diegetic and non-diegetic, though the latter is more common.
For example, diegetic music might be playing on a radio near the characters or on instruments. Non-diegetic music would be overlaid in post – completely unheard by the characters in the narrative.
It should also be noted that the source of diegetic sound doesn’t have to be on screen. The sound of rain outside or distant ambulance sirens is still diegetic, even if the object causing the noise is never filmed directly.
Hard or Spot Effects
Hard or spot effects are any sounds that are dependent on a diegetic action or event within the narrative.
Often, they’re matched up with a visual action, such as a car door slamming or a gun being fired. This creates the illusion of the sound being produced by the action, even if it was overlaid in post-production.
This is necessary because capturing all sounds on-set and live in high quality is often difficult.
Sometimes, a sound isn’t possible to film during a film shoot. For example, if you need a gunshot sound while using a prop, a non-functioning gun.
Mixed with special effects, spot SFX is great for creating the illusion of something happening even if it wasn’t actually performed on set.
Background Sound Effects
Background effects are also sometimes called soft or ambient SFX.
They are anything that plays in the background of a scene, usually to create ambiance or help build up the setting’s realism.
For instance, this could be birdsong in a park, rainfall against a car roof, or distant dogs barking and sirens in the city.
Layering these ambient sounds is a large part of creating a believable setting for your film.
As we experience the world, we’re constantly surrounded by background sounds of all kinds. When a setting we see in a film doesn’t have them, it can feel hollow and fake.
Foley Sounds
These are sounds found in practically every film or video. They’re created and/or recorded by a foley artist who collects a library of sounds suitable for use throughout the film.
Anytime a sound effect is added to punctuate an action or create the illusion of something happening, it’s likely a Foley effect. This could be footsteps in the snow, distant thunder, or glass shattering on a floor.
In the past, the visual capabilities of a film were limited by what could be made from physical props or extremely primitive VFX. Now, we can create almost any type of SFX, real or fiction.
As a result, audio also has had to keep up. As fictional things are created visually, they need sounds to accompany them.
This raises some of the most important questions a foley artist must answer: what does a dragon sound like? What about alien blasters?
Foley artists use countless creative techniques to modify or create SFX to match these non-existent visuals.
Designed Sound Effects
Unlike Foley effects, designed SFX is completely artificial in nature.
Designed sound effects are created using various sound design techniques that utilize studio equipment, synthesizers, and audio effects. These SFX sounds are generally intended for use in sci-fi, horror, thriller, and blockbuster movies.
Due to their sound design origin, designed SFX tends to have a distinctly modern and sometimes futuristic feel.
The trailer I created for my Inferno SFX sound library (embedded above) shows how designed SFX can turn a collection of short scenes into a coherent movie trailer storyline.
Off-Screen SFX
Off-screen sound effects refer to any SFX that happens off-screen, out of view of the audience.
The most common use of this is off-screen sirens, shouting, or dogs barking. There is some crossover with background effects, though off-screen effects are usually more relevant to the active story events on screen.
They are a great way of implying a story event without having to describe or show it strictly.
For instance, shouting voices and barking dogs can be an excellent way of suggesting the main character is being pursued while building tension.
Walla Sound Effects
Often known as Walla, this type of SFX refers to murmured background voices.
The words spoken in Walla aren’t audible. Instead, these voices are intended more as background sounds than functional dialogue. They become part of the scene rather than informing the viewer by what they say.
For example, they might be a cheering crowd, a whispering group, or the chatter of a busy room.
The Importance and Impact of SFX in Video Production
Now that we’ve covered some of the technical details of sound in film and video production, we can move on to how they contribute to the overall effect of a film.
There are a few major ways that SFX improves a film, notably through adding realism, enhancing storytelling, and creating emotional impact.
A film is nothing but layered elements, both visual and auditory. By layering these aspects over each other, you’ll achieve the maximum potential of your video – something that isn’t possible with visuals alone.
Ideally, visual and audio information in a film will support and enhance each other.
Creating Realism and Authenticity with SFX
This is one of the main purposes of audio in a film or narrative video. By layering the right audio over your scene, you can bring the world of the film to life – far more than you can with solely visuals!
When we interpret the world around us, we don’t just do so with our eyes.
Sound is a large part of how we collect information about our environment. In the same way, it’s a large part of the audience’s impression of the narrative world you create.
If your video shows a nighttime scene of a city without environmental SFX, it will feel lifeless. To create the feeling of a realistic city at night, you should layer sounds like sirens, dogs, cars, and other city sounds over the visuals.
You may not consciously notice these things while you’re watching, but you definitely will notice if the SFX is not there!
Attention to detail is what makes movies believable. Each tiny detail doesn’t do much on its own, but combined together, they make a scene feel real and fully fleshed out.
Interestingly, using SFX to create a feeling of realism doesn’t always mean using strictly realistic sounds.
Realistic sound effects often don’t have the same impact on-screen as non-realistic ones. In fact, we’ve become accustomed to many unrealistic sounds in films and TV – so much so that they feel realistic even if they aren’t!
For example, a real sword pulled from a sheath doesn’t make the sound you hear in shows like Game of Thrones. Likewise, a real gun makes more of a pop sound than an explosive bang.
Yet, if you use real gun sounds instead of processed SFX in a movie, they sound thin and fake.
In an interview, iconic sound designer Ben Burtt mentions that he starts with realism when choosing his sounds.
However, realism doesn’t feel right at times. In these cases, you must abandon the real for the fantastical, paradoxically making the film feel more genuine because it impacts your audience more effectively.
I design sound effects with a natural-sounding timbre but layer them with additional noises to make them sound more modern and cinematic.
Enhancing Storytelling
Most storytellers will know the eternal struggle of giving exposition to their audience without boring them to death.
It’s incredibly hard to add exposition in a way that feels natural and doesn’t slow the pace of the film to a crawl. A common mistake made in stories is having a huge, dialogue-based info dump right at the start.
So how do you tell pieces of your story to the audience without dumping it via dialogue?
SFX is the key!
SFX gives you a shortcut to telling narrative beats that would normally require dialogue, narration, or on-screen information. Sounds allow you to quickly and naturally establish a scene’s mood, setting, and atmosphere.
For instance, you may have the distant sirens of police approaching your characters’ crime scene, building tension that they may get caught.
There may be muffled voices behind a door and shouting from the apartment upstairs to depict the close quarters of city living.
Humans are creatures of nonverbal communication, even if we aren’t aware of it. This doesn’t just include body language but audio as well.
Adding the right sounds to a scene can intensify its impact on the audience and further engage them in the story.
For instance, the sharp zing of a bullet flying past a character’s head, an ear-shattering explosion close by, or even the slam of a door after an argument all create a stronger sense of drama.
You could tell the same story without these sound effects, of course. However, it wouldn’t have the same impact and would feel flatter, less meaningful, and less engaging.
Creating Emotional Impact with Sounds
Creating emotional impact segues into the next major effect of great audio design in a film.
It’s easy to tell how music impacts our emotions, especially when paired with the right story and visuals. However, SFX can do the same – sometimes even more.
It’s easy to miss this effect while watching. When done well, SFX should blend seamlessly with the rest of the art form – becoming a subconscious influence on the audience.
We often don’t notice SFX because it’s seamlessly interlaced with the visuals, becoming a single entity.
A favorite use of SFX to heighten the feelings of the visuals is in horror films, where the anxiety-inducing notes of a string instrument almost always accompany a jumpscare.
The scare on its own is fine and frightening, but it becomes downright heart-pounding when paired with cinematic sound effects like impacts and booms.
Tension is also intrinsically linked to sound.
You can raise tension, even in a scene that seems innocuous on its own, by having a rising tone or constant, thrumming note that suggests something is about to happen.
A popular choice for this is a sound effect called Shepherd’s Tone. This particular sound always seems like it’s getting higher and higher in pitch, but it’s actually an endless loop of the same sound.
The result is a sound effect that makes us anxious because it constantly feels like it will soon reach its inevitable climax, but it never does!
The Shepherd’s Tone is often used in films to put the audience on edge subconsciously. A famous example is the movie Dunkirk (2017).
SFX can be used to heighten emotions in the film outside of fear and tension, too
For instance, rising birdsong can create a feeling of hope, especially if a character is just emerging from a terrible or scary experience.
Water sounds like ocean waves can have a calming or intensifying impact on a scene, depending on the context.
An encroaching thunderstorm sound rumbling in the distance creates a feeling of foreboding.
Case Studies and SFX Examples
Now that we’ve discussed the ins and outs of SFX, let’s break down a couple of examples from famous films and discuss their use of sound design.
If you want to create similar sound effects, it’s important to look at the process of successful pieces and analyze them closely.
If you can understand how the greats put their art together, you can use these techniques in your own work as well.
Jurassic Park (1993)
Director: Steven Spielberg
Sound Designer: Gary Rydstrom
The T-Rex Paddock scene is iconic! It’s an incredible amalgamation of groundbreaking special and sound effects work, creating a scene that stands up even 30 years later.
This is the first real moment of terror in Jurassic Park. It’s our introduction to the dinosaurs, the “monsters” of the film, and what will be chasing our protagonists around for the next hour.
It’s important that Spielberg got this right; if this moment doesn’t make the prehistoric beasts terrifying, the rest of the film probably won’t either.
A monster in any movie is at its scariest when we know little about it.
Our imaginations will always conjure scarier things than any director could put on screen, so this first reveal of a monster is when fear will be at its highest in the audience.
As such, it must be handled with extreme care. This example is a masterclass in monster introduction.
The first thing you should note about the T-rex scene is that there is absolutely no music.
This isn’t normally the case in this film, with some of the most iconic movie music ever placed elsewhere. However, the SFX takes center stage alongside the incredible practical effects here.
There’s silence, only the rainfall against the roof of the cars. This purely diegetic soundscape is paired with the complete, isolating darkness outside.
Music is human, and there are no humans here besides our protagonists. They are utterly alone.
Then, a distant thud sound effect.
Silence. Rain. No character seems to have noticed except Tim, the young boy. Was there really a sound? Did you mishear?
Another thud. Closer this time. Deep and echoing, something huge.
Then, another. This time it’s paired with the bone-chilling visual of the cup of water on the dashboard, rippling with each noise. More characters have noticed now.
The tension rises in the chilling silence, sending your heart leaping into your throat with each thud.
The silence between each SFX is just long enough that you start to wonder if it’s stopped and if the monster has left. Then, another thud – it’s even closer now.
Even knowing exactly how this scene goes (having watched it dozens of times), I still feel the rising tension of this moment! It’s incredibly well done, both in visuals and audio.
The audience shares in the slowly dawning horror of the protagonists as they realize what’s happening and what is inevitable.
Then, the visual cue of the missing goat, followed by a strategic moment of silence that lets your anxiety build just enough, and – THUD. The goat’s leg hits the car roof.
This is the final explosion of the tension that has been building for so long. With Lex’s scream, chaos is released, and the SFX of the scene picks up massively.
We finally see our monster: the T-Rex, and she gives an iconic roar sound effect.
This roar is an excellent example of the creativity required of sound designers, especially when creating audio for something that doesn’t exist in real life, such as a dinosaur.
Rydstrom spent weeks searching for the perfect base sound to create the dinosaur SFX. Eventually, it was found in the trumpet of a baby elephant. This was pitch-shifted, then overlaid with noises from alligators and the blowhole of a humpback whale.
All of these things combine into the perfect sound for this monstrous theater icon. Now, it can hardly be imagined any other way.
Rydstrom mentioned in an interview that this entire scene was written around sound, not visuals.
SFX truly are the stars of this moment. Sound effects carry the major emotions far beyond what could have been achieved by showing the T-Rex immediately.
Star Wars (1977)
Director: George Lucas
Sound Designer: Ben Burtt
Star Wars is another film series filled to the brim with iconic sound effects – so recognizable that many people could tell you what they are with sound alone.
Generally, when people discuss the sounds of Star Wars, they talk about the lightsaber SFX.
These are really interesting examples of Foley sound development. Burtt worked on this film right out of college and had worked in their projection studio just before graduating.
He had come to love the steady hum of the classic projectors firing up, and once he heard about the lightsabers he needed to create audio for, he knew it was perfect.
Burtt recorded the raw sound of the projector, then modified it with white noise from a television.
To create the sound of moving lightsabers, he used a speaker to emit the sound he’d created and physically swung it around a room, recording it once again with the added Doppler effect from the movement.
Thus, the classic sound effect – the SFX of a moving lightsaber – was born.
Notably, there aren’t any lightsabers in the scene embedded above. Instead, it has one of my favorite, lesser-known uses of sound design in the original Star Wars.
In the original trilogy, there is a constant, thrumming beat anytime a shot is inside the Death Star.
It’s like a heartbeat, but incredibly low frequency so that it blends into the background. It’s never pointed out within the film – but it’s always there.
It’s like the heartbeat of a giant beast and is often paired with other deep grumbling and hisses to create the illusion of a living creature surrounding the scene.
This makes the huge space station feel alive, even if the effect is only subconscious. It makes the Death Star that much more intimidating – like a huge, unstoppable, living force that our protagonists must somehow defeat.
We also get a great example of Vader’s breathing in this scene – another classic SFX.
This helps to tell his story, even before it was fully fleshed out in the prequels. It illustrates the countless life support systems built into his suit, keeping him alive.
It’s a great example of incredibly deep storytelling without a single word being spoken by any character.
It also makes Vader constantly present in his scenes, even when he isn’t visible on screen. You can always hear him breathing, which adds even further to his intimidating, powerful presence.
In almost every Star Wars scene, you’ll see how SFX and music can move flawlessly as one as if they’re in a dance.
The beats of the music place themselves perfectly between major SFX moments. This entire sequence constantly bounces between chaos and tense silence, using SFX in the former and music in the latter.
This dance guides the viewer’s emotions to match those of the characters.
SFX – The Bottom Line
Audio should not be dismissed as a tool of filmmaking.
If you’re telling a story on screen, SFX is just one crucial tool in your collection – but it can also have a huge impact. Without it, you dull every other part of your storytelling.
One of my favorite things about sound design in film is that there isn’t just one strict, correct way.
Much like cinematography or writing, there are a thousand ways to do it and a thousand rules you can break in creative ways to create something completely unique.
Often, those rulebreakers become the guidelines for the next generation of film.
Be creative, think beyond tradition – and most importantly, understand your craft as any other. You are building an elaborate lie, as a sculptor builds with clay.
In any sculpture, detail is the final touch that breathes life into the figure. Getting the basic shapes is important, but they mean nothing unless you do that final pass of detail. The little things matter.