unity-rc-audio

name	unity-rc-audio
description	Unity RC Audio

Unity RC Audio

Use this skill when implementing audio for an RC car racing game. RC cars sound nothing like full-size vehicles -- brushless motors produce a high-pitched whine, not engine rumble. Covers motor audio synthesis, RPM crossfade, ESC/servo/tire/impact sounds, AudioMixer architecture, Doppler configuration, opponent audio LOD, and compression settings.

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AudioSource Setup Table

Reference table for configuring each sound source:

Source	Clip Type	Spatial Blend	Min Distance	Max Distance	Loop	Priority
Motor	Sampled loops	0.95	1m	20m	Yes	0 (highest)
Servo	Short loop	0.9	0.5m	5m	Yes	64
Tires (roll)	Surface loops	1.0	0.3m	10m	Yes	32
Tires (slip)	Scrub loop	1.0	0.3m	10m	Yes	32
Wind	Noise loop	0.0 (2D)	—	—	Yes	128
Impact	One-shots	1.0	0.5m	15m	No	16
ESC Melody	One-shot	0.8	1m	10m	No	64
Ambient	Long loop	0.0 (2D)	—	—	Yes	200

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Compression and Loading Settings

Audio Import Settings

Clip Type	Load Type	Compression	Force Mono	Sample Rate
Motor loops	Decompress on Load	ADPCM	Yes (3D)	44100
Servo loop	Decompress on Load	ADPCM	Yes (3D)	22050
Tire loops	Decompress on Load	ADPCM	Yes (3D)	22050
Impact clips	Decompress on Load	ADPCM	Yes (3D)	44100
ESC melody	Decompress on Load	PCM	Yes (3D)	44100
Wind loop	Decompress on Load	ADPCM	No (2D stereo)	22050
Music	Streaming	Vorbis (quality 70%)	No (stereo)	44100
Ambient	Streaming	Vorbis (quality 50%)	No (stereo)	44100

Key Rules

• Force to Mono on ALL 3D spatial sources — stereo 3D audio wastes memory and sounds wrong
• ADPCM for short/medium clips: 3.5:1 compression, low CPU decode cost, good for loops
• PCM (uncompressed) for very short clips that need perfect fidelity (ESC melody)
• Vorbis Streaming for music/ambient: saves memory, slight CPU cost for decode
• Never stream short clips — the overhead of streaming is not worth it for clips under 5 seconds
• Decompress on Load for gameplay-critical sounds to avoid decode latency

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Middleware Decision Guide

Project Scale	Recommendation	Reasoning
Indie / small team	Unity native AudioMixer	Sufficient for RC racing needs, no licensing cost, simpler pipeline
Dedicated audio designer	FMOD	Better authoring tools, runtime parameter binding, event-based workflow
AAA / large team	Wwise	Full-featured but heavy integration cost, overkill for most RC games

For this project (R8EO-X), Unity's native audio system with AudioMixer is the recommended starting point. The sound design is focused (one vehicle type, limited surface types) and does not require the advanced features of middleware.

If audio complexity grows (multiple vehicle classes, dynamic weather affecting sound, complex music systems), consider migrating to FMOD. The abstraction layer in the code examples above makes this migration straightforward — swap AudioSource calls for FMOD event triggers.

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Free CC0 / Creative Commons Sound Sources

Sound	Source	Notes
RC brushless motor	Freesound: "RC motor" by noiseloop	Record at multiple RPMs, loop points
Servo whine	Freesound: "servo" by plingativator	Short loop, pitch-shift to taste
Plastic/Lexan crash	Freesound: "plastic crash" by SwiftVector	Layer 3-5 variations
General impacts	Kenney Impact Sounds pack	CC0, game-ready, good variety
Bulk SFX library	Sonniss GDC Audio Bundle (annual)	Free yearly pack, thousands of sounds
Tire sounds	Freesound: search "small tire" or "RC tire"	Pitch-shift full-size samples up if needed
Wind/ambient	Freesound: search "outdoor wind loop"	Trim to seamless loops

Recording Your Own

If you have access to a real RC car:

• Record motor at 5 fixed throttle points (idle, 25%, 50%, 75%, 100%) for 10+ seconds each
• Record from 1 meter distance with a directional mic to minimize ambient noise
• Record impacts by dropping the car from increasing heights onto different surfaces
• Record servo by sweeping steering lock-to-lock at different speeds
• These recordings, properly looped, will sound more authentic than any library source

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Common Mistakes

1. Using ICE/car engine sounds on a brushless motor — Brushless motors whine, they do not rumble. Full-size engine samples sound completely wrong on an RC car regardless of pitch shifting.

2. Enabling Doppler on the player's own car — The camera tracks the player, so relative velocity is near zero. Doppler creates distracting pitch wobble with no realism benefit.

3. Setting maxDistance too large on spatial sources — An RC car is small and quiet. Motor audio should not be audible beyond 20m. Servo audio beyond 5m is unrealistic.

4. Using stereo clips for 3D spatial sources — Unity's 3D spatialization requires mono input. Stereo clips on 3D sources waste memory and produce incorrect spatialization.

5. Streaming short clips — Streaming adds decode latency and CPU overhead. Only stream long files (music, ambient beds). Short clips should use Decompress on Load.

6. No impact sound variation — Playing the same clip on every collision is immediately noticeable. Always use 3-5 variations with random selection.

7. Linear volume sliders — Human hearing is logarithmic. A linear 0-1 slider mapped directly to volume makes the bottom 50% of the slider nearly inaudible. Always convert to decibels.

8. Single tire source for all surfaces — Different surfaces sound dramatically different. At minimum, swap clips when the surface changes. Better: crossfade between surface-specific sources.

9. Forgetting motor strain audio — A motor at full throttle going uphill sounds different from full throttle at top speed. Load-dependent audio adds significant realism.

10. PlayClipAtPoint for impacts — Creates and destroys a GameObject every call, generating garbage and GC pressure. Use a pooled AudioSource system instead.

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Related Skills

Skill	When to Use
unity-audio-systems	General Unity audio architecture patterns
unity-physics-3d	Physics data (collision impulse, surface detection) that drives audio
unity-performance-optimization	AudioSource pooling, LOD strategies, memory budgets

Topic Pages

• Brushless Motor Audio
• Tire / Surface Audio
• Opponent LOD Audio
• Implementation Priority
• Servo Audio
• Doppler Effect