Appendix A: Glossary

AmbientEmitter: Pooled persistent looping voice managed by the propagation subsystem. Bypasses the SFX voice pool; routed through an AudioMixerGroup.

AmbientSource: Component declaring “there is an ambient bed in this zone with this clip.” Doesn’t play audio directly — the propagation manager drives a pooled AmbientEmitter on its behalf.

AudioContainer: ScriptableObject defining how audio clips are organized and played

AudioEvent: ScriptableObject triggering audio actions

AudioHandle: Control interface for single voice playback

AudioMultiHandle: Control interface for multi-voice playback

AudioPortal: Propagation subsystem edge — connects two AudioZones and models an opening (door, window, archway) with transmission and low-pass cutoff driven by an optional IPortalDoorSource.

AudioVoice: Single playing audio instance

AudioZone: Propagation subsystem node — a volume of world space tagged as one acoustic room. Supports multiple BoxColliders for L-shapes.

Bus: Volume control group in hierarchical structure

Crossfade: Smooth transition between two containers

Decibel (dB): Logarithmic unit of volume

Ducking: Automatic volume reduction of target buses

DSP Time: Digital Signal Processor time for sample-accurate scheduling

GainStack: Layered volume control system

IPortalDoorSource: Interface any MonoBehaviour can implement to drive an AudioPortal’s open/closed state. Decouples propagation from any specific project’s door system.

Instance Limiting: Maximum concurrent playbacks of same event

LOD: In this system, the enableLOD switch for voice virtualization: once more than Max Real Voices are live, the least important voices are paused and tracked. There are no distance tiers.

Multi-Position: Synchronized playback across multiple emitters

Occlusion: Raycast-based sound blocking

Portal: See AudioPortal.

Priority: Voice stealing priority (Low, Medium, High, Critical)

Propagation: Zone/portal graph-based routing of long-running ambient beds through world geometry.

PropagationManager: Singleton orchestrator of the propagation subsystem. Owns registries, the solver, and the emitter pool. Auto-instantiated on first reference.

RTPC: Real-Time Parameter Control, dynamic audio parameter. The string API (SetRTPC) sets a parameter’s global value by name (§3.4)

Parameter: A number the game sets and sounds read (RPM, speed, intensity). Defined by a Parameter asset (unit, range, default) or by name (§3.4)

Scope (parameter): Where a parameter value is stored: one play (a handle), one emitter, or global. A sound reads the first that has one

Audio Emitter: A component for an object that makes sounds (a car). Sounds posted on it read its parameter values

Listening point: Where the game listens from, usually a camera, registered with AudioManager.AddListeningPoint. Pepper’s distance-based features use it instead of searching the scene; with Spatial Mode = Pepper several weighted points pan and attenuate every 3D sound (split screen) (§9.3)

Spatial Mode: Who pans and attenuates 3D sounds: Unity (the default, from its AudioListener) or Pepper (from every listening point) (§9.3)

Smoothing (slew): How fast what sounds hear follows a newly written parameter value: Ease (seconds to close 95% of the gap) or Rate (units per second), set on the Parameter asset (§3.4)

State: Game mode affecting multiple audio parameters

Switch: Conditional container selection

Virtualization: Pausing a voice to save a real AudioSource while keeping its place in the clip, so it comes back where it would have been

Voice: Playing audio instance

Voice Stealing: Stopping voice to make room for higher priority

Zone: See AudioZone.