Chapter 4: Audio Cues

Created by Sarah Choi (prompt writer using ChatGPT)

Audio Cues (Engine Classes, Servo Whine, Impacts)

Partnering with Gameplay, Physics, Animation, VFX & Audio

Vehicle audio is the invisible rig: it sells mass, motion, and material long before the model fills the frame. Concept artists influence this earlier than they realize by deciding where engines breathe, where gears mesh, and where materials will scrape or resonate. Production artists then translate those decisions into sockets, parameters, and mix notes that Sound can trust. This article explains how to think about engine classes, servo whine, impacts and scrapes, and how to tie audio to metrics and interaction so players hear the same truth they see, written equally for concept‑ and production‑side vehicle artists.

The first discipline is to anchor sound design to a metric sentence. Declare width, height, clearances, approach and departure angles, turn radius, nominal ride height, suspension travel, maximum speed, and key deployables such as landing gear or ramps. These numbers inform the rhythms and thresholds that audio will key off of: idle RPM bands, gear change points, brake squeal onset, and impact energy levels. When concept publishes a one‑paragraph role statement and metrics, audio can begin layering a believable soundscape in parallel with modeling and rigging.

Engine class is the backbone of the palette, and each class has a signature envelope that can be predicted from design. Internal‑combustion gasoline engines read as bright and rev‑happy with pronounced intake roar and exhaust bark; diesels read darker with stronger low‑frequency pulses, turbo hiss, and load‑dependent clatter; turbines read as smooth broadband rush with tonal whine that scales with spool rather than road speed; electrics read as clean torque with inverter whine and tire prominence; hybrids interpolate between two worlds and must avoid awkward layer handoffs. Concept influences this by locating intakes and exhausts, specifying mufflers or resonator volumes, and exposing heat vents. Production turns those choices into sockets with names and axes so Sound knows where to place sources and how to pan them during motion.

Idle, throttle, and overrun are the three states a player will hear most, and their transitions define character. Idle should carry identity at camera distance without being fatiguing; a light wobble or misfire in a scavenged street buggy tells a different story than the glassy hum of a military turbine. Throttle states should grow in both pitch and density as load increases, with a meaningful mid‑band where players spend time instead of saving all drama for redline. Overrun, the moments when throttle lifts and mass continues, is where character can sing: exhaust burbles on gasoline power, turbo chirps on diesels, faint generator whine on electrics. The concept sheet can hint at these by describing role and temperament, while production defines parameter curves—RPM, throttle, load, gear index—that control layer gains.

Servo whine and actuation belong to anything that deploys, tilts, or tracks. Landing gear doors, canopy lifts, turret traverses, vectoring nozzles, and flap actuators all sound different depending on speed, torque, and isolation. A sealed, well‑engineered bay will give muted hydraulic hiss and rubbery chuff; an exposed mechanized arm will click, rattle, and whine in the open air. These cues must respect rig timing and joint limits. If a door takes 0.8 seconds to clear a hinge envelope, the hiss cannot last 1.5 seconds without breaking trust. Put sockets at hinges, pistons, and lock points, and annotate dwell states such as uplock and downlock so Sound can drop tactile confirmations: a sharp metallic catch when gear seats, a softer latch for maintenance hatches. Concept can signal material and exposure; production encodes precise joint names and coordinates.

Impacts, scrapes, and debris are the punctuation marks that tell players how hard they are pushing the machine. Their credibility lives in metrics. Approach and departure angles dictate when skids will kiss ramps; breakover angles predict belly scrapes on humps; curb height sets the threshold for wheel thumps and tire yelps. A clean collision hull paired with named sockets at skid plates, tow eyes, and bumper corners lets Sound spawn one‑shot samples at the exact points of contact. Layering logic should change by surface: gravel adds a rain of micro‑pings, steel grating rings with a repeatable pitch, mud thuds and then muffles tire noise. Production can attach material tags to collision primitives and provide short notes about expected contact speeds so Sound can map dynamics without guesswork.

Occlusion and perspective complete the illusion. Interior versus exterior reads matter even in third‑person games, because cameras often cut close to cabins or bay interiors. Concept can design baffles and vents that imply how much engine and road noise leaks; production can measure effective wall thickness and provide a crude occlusion map that Audio turns into low‑pass filters and level changes. Doppler shifts should be subtle and applied mostly to fast pass‑bys; the more important cue is distance falloff that tracks the camera and avoids pumping when cameras swap sides. If a vehicle has an open deck or exposed intake, call that out in the sheet—open geometries leak high‑frequency detail and make directionality sharper.

Synchronization with VFX and Animation makes the machine feel single. Downwash needs rotor slap whose period and intensity correlate with blade passage frequency and throttle; contrails need a high‑frequency hiss that grows with angle of attack and humidity cues; exhaust flame wants a soft chuff at ignition and a roaring broadband layer for afterburn. Door hisses should precede motion by a breath, latches should land precisely when the rig’s lock toggles, and brake squeal should ramp when slip ratio crosses a threshold. These are not expensive to achieve when concept and production publish a shared set of parameters and when sockets share names across disciplines.

Mix and loudness standards keep excitement from turning into fatigue. A wide dynamic range can be thrilling in a trailer but exhausting in a session. Concept can help by avoiding designs that demand constant screaming layers to read; a quieter intake route or a better muffler volume can improve mix headroom without hurting identity. Production should deliver loudness targets and reference mixes for classes of vehicles—light wheeled, heavy tracked, rotorcraft, jets—so Sound can maintain consistency across a roster. Side‑chain ducking on UI beeps during critical events and gentle crossfades when cameras warp are better than abrupt mutes that make players distrust the mix.

Telemetry is the bridge that makes audio systemic rather than scripted. The minimum parameter set that most vehicles can expose includes speed, engine RPM or equivalent spool, throttle and brake inputs, gear index, suspension compression per corner, slip ratio, angle of attack for aircraft, gear door and strut positions, flap or spoiler deflection, damage tier, and water depth or dust level for biomes. When concept publishes which of these matter to the read and production binds them to sockets, Sound can drive layers from numbers instead of fragile animation events.

Accessibility and clarity should be part of the brief. Some players mix at low volume or on tiny speakers; others rely on subtitles or haptics. Concept can preserve signature rhythms that survive low‑fi playback, such as a distinctive two‑beat surge at spool or a latch click before a heavy thump. Production can provide optional visualizers for critical audio cues—simple emissive flicks synchronized to gear lock, brake temperature gauges that correlate with squeal—and ensure subtitles describe mechanics rather than only mood: “Left gear uplock engaged” conveys more than “clunk.”

Case studies illustrate how the pieces fit. A light recon buggy with a gasoline engine uses a bright intake and barky exhaust with gravel chatter that rises on slip. Servo cues include a quick winch motor for a small drone bay and a cheerful latch tick on doors. Impacts map to skid plate and bumper sockets, and brake squeal only appears above a speed threshold to avoid comic slow‑speed chirps. A tiltrotor troop carrier layers turbine rush with blade slap that enters at certain throttle and angle of attack bands, plus hydraulic hiss for bay doors and a satisfying hook when gear uplocks. Downwash noise scales with throttle and altitude, and interior occlusion dampens high‑frequency slap when the camera is within the cabin volume. A fast patrol boat blends diesel throb with prop cavitation under hard acceleration, spray hiss along chine sockets, and hull slaps that trigger at wave height thresholds; when the boat pitches, an engine mount groan layer rises briefly to sell strain.

A disciplined handoff prevents drift. The audio plate set should include a hero three‑quarter view for context, orthos with labeled audio sockets, a table of parameter names and ranges, a short mix note, and an occlusion note distinguishing interior and exterior. Units and axes should match the project standard and sit on every plate. A risk note can flag unresolved questions such as hybrid handoff transitions or rotor slap periodicity. When these documents live alongside VFX and rig specs, the soundscape grows from the same skeleton and the vehicle arrives in engine sounding like it looks.

The closing principle is simple: audio is structure made audible. If the concept shapes air paths, moving joints, and materials with sound in mind, and production exposes sockets and parameters with rigor, then Sound can compose layers that obey physics and story. Engines breathe from the right places, servos complain at believable moments, impacts land exactly when the metrics predict, and the machine becomes a character players can listen to as well as watch.