Create any acoustic space from scratch — from realistic rooms to creative reverbs, with full control over every reflection.

Reverb is fundamental to how we perceive sound. Every acoustic experience we have — from intimate conversations to concert hall performances — includes the reflections and resonances of the space around us. When we produce audio for reproduction through speakers or headphones, we need tools to create these spatial impressions artificially.

The industry has settled on two dominant approaches, each with significant limitations.

Algorithmic reverbs use mathematical models to simulate room acoustics. Early designs were based on feedback delay networks and allpass filters — clever approximations that could run on limited hardware. Modern algorithmic reverbs add sophistication, but they remain approximations. The parameters rarely map to physical room characteristics. "Size" and "decay" interact in non-obvious ways. Achieving a specific acoustic result requires trial and error rather than informed design. And when you need to change something — make the room a bit brighter, adjust the early reflection pattern — you're back to twiddling abstract knobs hoping to land somewhere useful.

Convolution reverbs take the opposite approach: capture the impulse response of a real space, then convolve incoming audio with that measurement. The results can be stunningly realistic — you're literally replaying the acoustic signature of an actual room. But convolution is inflexible. Want a longer decay? You need a different impulse response. Want to change the wall material? Record a new room. Want to adjust early reflections independently from the tail? Impossible — it's all baked into the IR. And the processing cost is significant: continuous FFT operations consuming CPU cycles and introducing latency.

Neither approach gives you what creative audio work actually demands: precise control over acoustic parameters, the ability to design spaces that don't exist in nature, and the flexibility to adjust any aspect of the reverb independently. Neither approach lets you think in terms of physical room characteristics — dimensions, materials, source and listener positions — while maintaining creative freedom.

VRA builds acoustic spaces from first principles, modeling the actual physics of how sound behaves in enclosed environments. Rather than approximating reverb characteristics with abstract algorithms or replaying captured impulse responses, VRA calculates reflections based on room geometry, surface materials, and source/listener positions.

The processing divides into three distinct stages, each handling a different aspect of room acoustics and each independently adjustable.

Early Reflections arrive first — the sound bouncing once off each room surface before reaching the listener. These early reflections are critical for spatial perception; they tell your brain about room size, shape, and your position within it. VRA calculates early reflections using ray tracing: for each surface, the algorithm computes the reflection path from source to surface to listener, applies the appropriate delay based on path length, and filters the reflection according to the surface material's absorption characteristics. The result is physically accurate early reflection patterns that change appropriately as you adjust room dimensions or move sources and listeners.

Cluster reflections follow — the denser pattern of second and third-order reflections that builds between the early arrivals and the diffuse tail. This transition region is crucial for reverb naturalness; get it wrong, and the space sounds artificial. VRA models the cluster using a simplified algorithm that captures the statistical behavior of multiple reflection paths without the computational expense of tracing every ray. The cluster density, timing, and spectral character derive from the room parameters you've set, maintaining physical plausibility while remaining computationally efficient.

Late reverb is the diffuse tail — the dense wash of reflections that defines the room's overall decay character. VRA generates late reverb based on your target RT60 (the time for reverb to decay by 60dB), shaped by the room dimensions and average surface absorption. Unlike algorithmic reverbs that abstract this into "decay time" and "damping" parameters, VRA's late reverb emerges from the room model. Change the ceiling absorption, and the late reverb changes appropriately. Adjust the room volume, and the decay time responds as physics dictates.

The entire processing chain is parametric — no FFT, no convolution, no block-based processing. VRA adds only a few samples of latency at any sample rate, making it suitable for real-time applications where convolution reverbs fail.

Three-stage architecture

Early reflections, cluster, and late reverb operate as independent processing stages. Adjust the early reflection level without touching the tail. Modify the cluster density without affecting the early pattern. Shape the late decay independently from the initial spatial impression. This separation, enables precise acoustic design impossible with other tools.

Per-surface material control

A room has six surfaces: four walls, a floor, and a ceiling. In reality, each surface might have different acoustic properties — carpet on the floor, glass on one wall, acoustic panels on the ceiling. VRA models this explicitly. Set absorption coefficients for each surface independently, and the reverb responds appropriately. The early reflections from the carpeted floor differ from those off the glass wall. The overall RT60 emerges from the combined absorption. You're designing a space, not tweaking abstract parameters.

Real physics foundation

VRA's calculations follow acoustic physics. The inverse square law governs level relationships. The speed of sound determines reflection timing. Surface absorption follows frequency-dependent models. When you set a room dimension in VRA, the acoustic result matches what that dimension would produce in reality. This physical grounding makes VRA intuitive for anyone who understands basic acoustics, and it ensures that results translate meaningfully between virtual and physical spaces.

Parametric processing

No FFT. No convolution. No massive CPU consumption. VRA runs on embedded platforms, mobile devices, and resource-constrained systems where convolution reverbs are impossible. The low latency enables real-time parameter changes — sweep a room dimension and hear the acoustic change instantly, without glitches or artifacts.

Source and speaker positioning

VRA knows where your sources and speakers are in the virtual room. Early reflections calculate based on actual geometric relationships. Move a source closer to a wall, and the early reflection from that wall arrives sooner and louder. Position speakers around the listener, and each receives appropriately calculated reverb for its position. This spatial awareness enables acoustic design that responds to your actual reproduction scenario.

RT60 targeting

Rather than guessing at decay time parameters, specify your target RT60 directly. VRA calculates the late reverb characteristics needed to achieve that decay time given your room dimensions and surface materials. If your material choices can't physically achieve the target RT60, VRA tells you — another benefit of physics-based processing.

Creative freedom

Despite the physical foundation, VRA doesn't restrict you to realistic spaces. Set absorption coefficients that don't exist in nature. Create rooms with impossible geometries. Design spaces where early reflections come from a small room but the tail suggests a cathedral. The physical models are tools for creativity, not constraints on imagination.

Early Reflections

The first reflections off room surfaces arrive within roughly 50 milliseconds of the direct sound. These early reflections carry critical spatial information: the size and shape of the room, the position of the source within it, and the listener's location relative to boundaries. Our auditory system evolved to extract this information; we instinctively understand spaces through their early reflection patterns.

VRA calculates early reflections using ray tracing. For each of the six room surfaces, the algorithm determines the mirror image position of the source, calculates the path from this image source to the listener position, derives the arrival time from path length and speed of sound, and applies filtering based on the surface material's absorption characteristics. The result is an early reflection pattern that responds accurately to room geometry changes.

You control early reflection level independently from the rest of the reverb. For some applications — dialog recording, close-miked instruments — you might want prominent early reflections that establish a sense of space without excessive tail. For others — atmospheric sound design, ambient textures — you might reduce early reflections relative to the diffuse tail. VRA makes this choice explicit rather than burying it in interacting parameters.

Cluster Reflections

Between the discrete early arrivals and the smooth diffuse tail lies a transitional region: the cluster. Second, third, and fourth-order reflections build in density, creating a pattern too complex to hear as individual events but not yet dense enough to perceive as continuous reverb.

This transition region defines reverb character more than most users realize. A cluster that builds too slowly sounds artificial — a gap between early reflections and tail. A cluster that's too dense too quickly sounds unnatural — the space seems smaller than its decay time suggests. Getting the cluster right requires matching its statistical properties to the room characteristics.

Cluster level is independently adjustable. For transparent reverb that doesn't muddy the source, reduce the cluster relative to early and late stages. For dense, immersive spaces, increase cluster presence. The choice is creative, and VRA makes it accessible.

Late Reverb

The diffuse tail is what most people mean when they say "reverb" — the dense wash of energy that decays over time, defining the room's overall acoustic signature. A concert hall has a long, smooth tail. A bedroom has a short, damped tail. The late reverb tells us whether we're in a cathedral or a closet.

VRA generates late reverb based on your target RT60, room dimensions, and average surface absorption. The algorithm creates a decay envelope and spectral character consistent with these parameters. Change the ceiling absorption, and high frequencies decay faster — as they would in reality. Increase the room volume, and the decay lengthens — as physics dictates.

Unlike algorithmic reverbs where "decay time" is an abstract parameter, VRA's late reverb emerges from the room model. This grounding in physics ensures consistent, predictable results. When you need a 2-second RT60 with natural high-frequency rolloff, you specify those characteristics directly rather than hunting through presets.

Geometric Parameters

Material Parameters

Each of the six room surfaces has an independent absorption coefficient ranging from 0.0 (perfectly reflective) to 1.0 (perfectly absorptive), through different frequencies. VRA applies these coefficients to reflections from each surface, affecting both the early reflection character and the overall RT60.

Target Parameters