How Procedural Audio Creates Sound

Procedural audio — sound generated in real time by a mathematical model rather than played back from a pre-recorded clip. Instead of triggering a fixed audio file when a car crashes or a foot lands on gravel, the game calculates a waveform on the fly from the specific material, force, and geometry of that exact moment. It is the difference between playing a photograph of a sound and running a small physics simulation that produces one.

Most sounds you hear in games, footsteps, gunfire, music, voice lines, are recordings triggered on cue. Procedural audio is the minority technique that instead builds the sound itself, sample by sample, from a set of rules and physical parameters. It solves a specific problem: some games generate so many possible situations that no team could ever record a distinct sound for each one, so the audio has to be computed instead of collected.

What procedural audio actually is

Sample-based audio is the default in game development: a sound designer records or synthesizes a fixed audio clip in a studio, imports it into the game engine, and the engine plays that exact clip back — sometimes with pitch or volume tweaks — whenever a matching event fires. A footstep sound is a footstep sound. It never changes shape, only how loud it is or how it's mixed with reverb.

Procedural audio skips the fixed clip entirely. The game runs a small audio synthesis algorithm at the moment the sound is needed, feeding it parameters that describe the event — the surface material underfoot, the mass and velocity of a colliding object, the caliber and barrel length of a weapon, the distance and orientation of the listener — and the algorithm outputs a new waveform calculated from those inputs. The Belgian-French audio researcher and engineer Andy Farnell, whose book "Designing Sound" (MIT Press, 2010) is one of the most cited academic references on the technique, describes procedural audio's core premise as treating sound as a process rather than as data (Farnell, "Designing Sound," MIT Press, 2010). A recording is a fixed piece of data. A procedural system is a running process that produces different data every time depending on its inputs.

This distinction matters because it changes what a sound designer's job looks like. In sample-based work, the designer's output is an audio file. In procedural work, the designer's output is closer to a small program: a set of rules, filters, and physical parameters tuned so the algorithm produces plausible, appropriate-sounding output across a wide range of inputs it will encounter during actual play, many of which the designer never explicitly tested by ear in advance.

Andy Farnell's "Designing Sound" (MIT Press, 2010) is built entirely around a philosophy summarized in its own framing: sound in games should be treated as a process, computed live from physical models, rather than as fixed data recorded once and replayed indefinitely (Farnell, 2010).

The synthesis techniques underneath the term

"Procedural audio" is an umbrella term. Underneath it sit several distinct synthesis techniques, most of which were developed decades earlier for electronic music production and computer music research before game engines adopted them.

Additive synthesis builds a complex sound by summing multiple simple sine waves, each with its own frequency, amplitude, and phase. Any complex waveform can, in principle, be decomposed into a sum of sine waves at different frequencies (this is the basis of Fourier analysis), so additive synthesis works by doing that process in reverse: starting from simple tones and layering them until the combined result approximates a target timbre. It gives precise control over harmonic content but is computationally demanding when many sine components are needed for a rich, natural-sounding result.

Subtractive synthesis works the opposite direction. It starts with a harmonically rich waveform, a sawtooth or square wave, or filtered noise, and removes frequency content using filters (low-pass, high-pass, band-pass) to sculpt the sound down to a target timbre. This is the technique behind most analog and virtual analog synthesizers, and it is computationally cheaper than heavy additive synthesis because subtractive synthesis manipulates one broadband source rather than summing many discrete oscillators.

Granular synthesis breaks existing audio, whether recorded or synthesized, into extremely short fragments called grains, typically a few milliseconds to a few tens of milliseconds long, and reassembles, overlaps, and manipulates those grains in real time to build new textures. It's a hybrid approach: still rooted in source material, but capable of producing output that no longer resembles the original clip once the grains are stretched, reordered, or layered densely enough. Granular techniques are common in ambient and environmental game audio, where a continuous, evolving texture (wind, water, engine drone) needs to vary indefinitely without looping in an audibly repetitive way.

Physical modeling synthesis is the technique most associated with convincing procedural game audio because it doesn't start from any waveform at all. It starts from a mathematical description of a physical object, its material stiffness, mass, resonant frequency, and how it dissipates energy through vibration, and calculates what sound that object would produce given a specific input force. A struck wine glass and a struck wooden block produce different sounds under physical modeling not because a sound designer recorded each one, but because the underlying equations account for how glass and wood actually vibrate and decay differently when struck.

How is procedural audio different from just pitch-shifting a recording?

Pitch-shifting, randomized sample selection, and volume variation still start from one fixed recorded waveform and modify it superficially. True procedural synthesis generates the waveform itself from underlying parameters like material and force, which is why it can respond correctly to combinations of inputs no one specifically pre-recorded, rather than just making an existing recording sound slightly different each time.

Why games need this at all: the combinatorial problem

The practical reason procedural audio exists is a production math problem. A sample-based sound library can only ever contain the specific combinations a sound designer thought to record in advance. The moment a game's systems allow enough variation, that library runs out.

Consider a driving game with a detailed vehicle-damage model. A car's crumple state can vary by impact angle, speed, which panel is struck, how many times it's already been damaged, and what it hits. Multiply even a modest number of options across each of those variables and the number of distinct possible crash events climbs into the thousands or millions, far beyond what any team could record and cleanly integrate as individual audio files without ballooning both production time and the game's installed size.

A destructible-environment game faces the same wall from a different angle. Sandbox physics titles that let players demolish voxel-based structures generate collision and destruction sounds procedurally in large part because the number of possible object collisions, spanning different materials, sizes, impact angles, and forces, is effectively unbounded. A fixed sample library can only cover the combinations someone anticipated; a physical model can respond, in principle, to combinations nobody explicitly planned for, because it's calculating from first principles rather than looking up a matching pre-made clip.

No Man's Sky is a documented real-world case of a studio confronting exactly this problem at a much larger scale: a procedurally generated universe with an effectively unbounded number of possible planets, creatures, and biomes. Audio director Paul Weir has described the game's approach as treating audio as "a way of organizing lots of small, granular bits of sound [and] music components, and imposing a bit of structure and logic and control on top of them" rather than authoring fixed tracks and clips for every possible generated environment (Weir, quoted in A Sound Effect interview on No Man's Sky's procedural audio and music system). The generative music system draws on granular and generative techniques precisely because a fixed soundtrack cannot scale to a universe whose content is itself generated on the fly.

No Man's Sky's audio director Paul Weir has publicly described the game's music and sound system as built from granular, recombinable components rather than fixed authored tracks, a direct response to the fact that the game's planets and creatures are themselves procedurally generated at a scale no fixed audio library could cover (A Sound Effect interview with Paul Weir).

What it sounds like, and why that's different from a recording

A recorded gunshot sample plays back identically every time, the same static waveform triggered on cue, however it's mixed or layered afterward. A genuinely procedural equivalent can shift its actual waveform based on real-time inputs: the listener's distance, nearby surfaces causing reflections, a weapon's simulated barrel length, producing a different output each time rather than the same file replayed at a different volume or with a different filter slapped on top.

Think of it as the difference between a photograph of one specific ocean wave and a physics simulation of ocean waves in general. The photograph captures a single real moment with perfect fidelity but can never show you a different wave. The simulation can never reproduce that one specific photographed wave exactly, but it can generate an effectively unlimited variety of physically plausible new waves that respond correctly as wind, depth, and obstacles change. Recorded samples are the photograph. Procedural synthesis is the simulation: less faithful to any one perfect reference, more capable of covering a space of possibilities nobody could fully anticipate and pre-shoot in advance.

A second useful analogy is language itself. A recorded sample library is like a phrasebook: a fixed set of pre-translated sentences that work perfectly for exactly the situations someone thought to include, and fail silently the moment you need something slightly different. A procedural synthesis model is more like actually knowing the grammar: slower to produce any single sentence from scratch, more computationally demanding, but able to construct a correct new sentence for a situation the phrasebook's author never anticipated.

Does procedural audio mean random noise?

No. A common misconception is that "procedural" implies unpredictable or randomly generated noise. In practice, procedural audio is calculated from a deliberately engineered mathematical model, tuned carefully by sound designers so it responds predictably and appropriately to specific inputs like material, force, and distance. Randomness, when it's used at all, is typically a small, controlled variation layered on top of a mostly deterministic physical model, not the core mechanism.

The real cost: why most games still use recordings

Procedural audio is not free, and its costs explain why it remains a selectively applied technique rather than a wholesale replacement for recorded audio.

Physical modeling and additive synthesis are computationally heavier per sound event than simply decoding and playing back a compressed audio file, because the game has to run the actual synthesis math in real time rather than streaming pre-computed samples off disk. On a system already budgeting CPU cycles for physics, AI, and rendering, that additional real-time audio computation competes for the same limited resources, especially when many procedural sound events (a large debris field, a crowd of NPCs) need to be calculated simultaneously.

Building a convincing physical model also requires specialized engineering and sound-design expertise that differs from traditional recording and editing. Modeling how a specific material actually vibrates, resonates, and decays convincingly takes iterative tuning against real-world reference recordings, and getting it wrong produces synthetic-sounding, unconvincing audio that a good recorded sample would have avoided entirely. That specialized skill set, plus the added engineering integration work of running live synthesis inside a game engine's audio pipeline, is a real production cost most studios weigh against the benefit.

Because of this cost, the dominant real-world pattern is hybrid, not purely procedural. A widely referenced example is EA DICE's approach to weapon audio on the Frostbite engine, where teams have described layering multiple recorded gunshot samples together and mixing them in real time based on distance, environment, and listener position, rather than synthesizing gunfire entirely from scratch (as described in game-audio industry coverage of Frostbite-era weapon sound design). That's procedural mixing and layering logic applied on top of recorded source material, a middle ground far more common in shipped AAA titles than pure synthesis.

Approach	Memory footprint	Variability	Typical use case
Sample-based (recorded)	High — every variation needs its own audio file on disk	Low — identical playback each time, aside from volume/pitch tweaks	Voice acting, music, signature weapon sounds, core audio identity
Hybrid (procedural mixing of recordings)	Moderate — fewer base samples, recombined and layered at runtime	Moderate — many combinations from a smaller sample pool	Weapon audio, ambient layering, most shipped AAA titles
Fully procedural (synthesis-based)	Low — no per-variation audio files, only a model and parameters	High — responds to combinations never explicitly authored	Footsteps across varied surfaces, destructible-object collisions, physics-driven crashes

Most shipped games sit in the middle row: procedural logic layered on top of a recorded sample base, rather than at either pure extreme.

Where procedural audio actually earns its keep

Procedural audio isn't applied uniformly across a game. It tends to concentrate in specific systems where the combinatorial-variety problem is sharpest and the payoff for solving it is largest.

Footsteps across varied, player-chosen terrain are a textbook case: a game with open traversal across gravel, wood, metal, water, and snow, at variable speeds and stances, has far more foot-surface-speed combinations than a reasonable sample library can cover without becoming repetitive to a player's ear within minutes. Destructible environments and physics-driven collision systems are the other classic case, exactly the kind of system that made Teardown's approach to destruction audio a useful example: fully destructible voxel structures generate an open-ended number of possible collision events that a fixed sample set simply cannot pre-cover.

Vehicle and engine audio is a longer-running historical example, and one that predates most modern procedural game-audio techniques by decades. Racing games have used real-time pitch-shifting of engine sample loops tied to simulated RPM since well before physical modeling synthesis became practical in consumer hardware, an early, simpler form of dynamically responsive audio that shares procedural audio's core goal (matching sound to a continuously varying game state) without the full complexity of a true physical model.

Environmental and generative music systems, as in No Man's Sky, represent a different application of the same underlying idea: instead of physically modeling an object's vibration, the system recombines granular musical fragments according to rules, producing music that varies indefinitely to match a procedurally generated world rather than looping a fixed authored score.

Common misconceptions worth clearing up

Beyond the "random noise" misconception addressed earlier, two other misunderstandings come up often enough to be worth naming directly.

The first is assuming procedural techniques have quietly replaced recorded audio across the industry. They haven't. Most commercial games still lean heavily on recorded samples for their core sound identity: voice acting, music, and signature effects designed to have a specific, polished, repeatable character. Procedural techniques are applied selectively, to high-variation systems where combinatorial coverage matters more than a single perfect authored tone, not as a wholesale replacement strategy.

The second is treating procedural audio as a purely modern innovation born from recent hardware headroom. It isn't. Physical modeling synthesis traces back to digital signal processing research from the 1970s and 1980s, well before it was practical to run in a real-time game engine, and simple procedural techniques like RPM-driven engine pitch-shifting predate today's more sophisticated physical models by decades. What's changed recently is available compute budget, not the underlying mathematical idea.

What this means

Procedural audio solves a production problem that recorded samples fundamentally cannot: covering an open-ended, combinatorial space of possible in-game events without a proportional increase in recorded assets or storage. It does this by generating a waveform in real time from synthesis techniques, additive, subtractive, granular, and especially physical modeling, rather than triggering a fixed recorded clip, which is why a well-built procedural system can plausibly respond to material-and-force combinations no sound designer explicitly anticipated. That capability comes at a real cost in computation and specialized engineering effort, which is why the dominant pattern in shipped games remains hybrid: recorded samples for a game's core identity, procedural logic layered on top for the systems, footsteps, destruction, physics-driven collisions, where variety genuinely outpaces what any sample library can hold.

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FAQ

Q: What is procedural audio?

Sound generated in real time through mathematical synthesis, such as physical modeling of how a specific material vibrates under a given force, rather than played back from a fixed pre-recorded audio file.

Q: How is procedural audio different from just varying the pitch of a recorded sound?

Simple pitch or volume variation still starts from one fixed recorded waveform and modifies it superficially. True procedural audio, especially physical modeling synthesis, generates the waveform itself from parameters like material and force, producing genuinely new output rather than modifying an existing recording.

Q: Why don't all games use procedural audio instead of recordings?

It requires significantly more real-time computation per sound and specialized engineering and tuning expertise to model materials and physics convincingly. Most shipped games use a hybrid approach, applying procedural logic selectively to high-variation systems while keeping recorded samples for core audio identity like voice and music.

Q: What kinds of game sounds benefit most from procedural generation?

Sounds involving many possible combinations, such as footsteps across varied surfaces, destructible-object collisions, and physics-driven crashes, benefit most, since pre-recording every possible combination of material, force, and angle is not practically achievable with a fixed sample library.

Q: What are the main procedural audio synthesis techniques?

Additive synthesis (summing sine waves), subtractive synthesis (filtering a harmonically rich source down to a target timbre), granular synthesis (reassembling short fragments of audio into new textures), and physical modeling synthesis (calculating sound from a mathematical model of an object's material and physics) are the main techniques, with physical modeling most associated with convincing real-time game audio.

Q: Is procedural audio a recent invention?

No. Physical modeling synthesis research dates back to digital signal processing work in the 1970s and 1980s, and simple procedural techniques like RPM-based engine pitch-shifting in racing games predate today's more sophisticated real-time physical models by decades.