Introduction to Custom Attenuation in Wwise

Sound localization in games relies on a precise interplay of volume, filtering, and timing cues. Among these, distance-based attenuation – how a sound’s loudness and timbre change as the listener moves away – is fundamental. Wwise provides a powerful curve editor that lets you go far beyond the stock linear or logarithmic falloff. By crafting custom attenuation curves, you can simulate real-world acoustic behaviors, create dramatic gameplay moments, and ensure players always know exactly where a sound is coming from. This guide will walk you through the underlying physics, the Wwise attenuation system, and a detailed, step-by-step approach to building and fine-tuning custom curves for precise sound localization.

Understanding Attenuation in Game Audio

Physics of Sound Propagation

In the real world, sound pressure level (SPL) decreases with distance according to the inverse square law: doubling the distance reduces intensity by about 6 dB. However, this ideal model is rarely accurate in outdoor or indoor environments. Air absorption, humidity, temperature gradients, and obstacles all alter the decay curve. Low frequencies travel farther than high frequencies, so a distant sound not only becomes quieter but also muffled. For game audio, replicating these nuances is key to convincing localization.

Why Default Curves May Fall Short

Wwise ships with several default attenuation shapes, including linear, logarithmic, and custom presets. While these work for many scenarios, they often lack the flexibility needed for specific game mechanics. For instance, a whisper that carries only a few meters, a distant explosion that remains loud but loses high frequencies, or a directional speaker that only projects sound forward. Generic curves treat all frequencies equally and ignore spatial filtering. Custom curves allow you to break those limitations.

The Wwise Attenuation System

Curve Types: Volume, LPF, HPF, Spread, Focus

Wwise attenuation curves are not just about volume. The system supports per-curve control over:

  • Volume (dB): The primary loudness curve over distance.
  • Low-Pass Filter (LPF): High-frequency rolloff – critical for occlusion and distant sounds.
  • High-Pass Filter (HPF): Low-frequency rolloff, useful for very close proximity effects.
  • Spread: How the sound is perceived in width; distant sources often feel narrower.
  • Focus: Affects the sound’s position accuracy in the surround field.

Each of these can have its own independent curve, giving you granular control over how a sound changes with distance.

The Curve Editor Interface

In Wwise, the Attenuation Editor presents a graph with distance on the X-axis (scaled to the maximum distance of the attenuation share set) and the parameter value on the Y-axis. You can add, move, and delete control points, and adjust curve shapes between points (linear, smooth, constant). The editor also supports multiple curves overlaid for comparison. Mastering this UI is the first step to creating custom behavior.

Designing Custom Attenuation Curves Step-by-Step

Step 1: Analyze Your Sound Sources

Before opening Wwise, consider the real-world analog of your sound. A small object dropping on grass will attenuate quickly and lose high frequencies fast. A thunderclap might maintain volume over kilometers but lose detail. Measure or estimate the audible range and the shape of volume loss. For gameplay, also consider design needs: maybe a sound needs to be audible only within a tight radius to encourage exploration, or it must stay loud but muffled for distant threats.

Step 2: Create a New Attenuation Curve

In your Wwise project, navigate to the Project Explorer and create a new Attenuation ShareSet (or edit an existing one). Inside the Attenuation Editor, click the Add Curve button and choose the type you want to edit (typically Volume first). Wwise allows you to have separate curves for different parameters, but they all share the same distance axis. Set the maximum distance to match the farthest point you want the sound to be heard.

Step 3: Set the Volume Over Distance

Start with the volume curve. For precise localization, avoid steep cliffs near zero distance – they cause unnatural pops. Instead, shape a gentle rolloff. For example, a curve that holds at -3 dB for the first meter (simulating near-field bass boost) then drops -12 dB by 5 meters, and -30 dB by 20 meters. Use smooth interpolation. The key is to balance realism with clarity: players must never lose the sound’s direction, so the volume should never drop below the listening threshold before other cues (like LPF) fade out.

Step 4: Add Filtering and Spatialization Curves

Once volume is shaped, add a Low-Pass Filter curve. As distance increases, increase the LPF (in Hz). A typical curve might start at 0 Hz (no filtering) and ramp up to 8,000–10,000 Hz at maximum distance. This mimics air absorption. For sounds that are very close or interior, an HPF curve (cutting lows) can simulate proximity to a wall or ground. Spread curves can narrow the perceived width as distance grows, which aids localization by making distant sounds appear as point sources. Focus curves can slightly push off-center sounds toward the center to prevent localization confusion in surround setups.

Step 5: Preview and Refine

Wwise includes a built-in 3D preview that lets you move a virtual listener relative to sources. Use this extensively. Listen for abrupt transitions, loss of directionality, or unnatural volume jumps. Pay attention to the interplay of curves: a large LPF drop without a corresponding volume reduction can make the sound appear “shut in a box.” Adjust control points until the sound smoothly transitions from clear and close to muffled and distant without losing its anchor point.

Advanced Techniques for Realism

Using Multiple Curves for Realism

Often a single volume curve is insufficient. For example, a helicopter rotor sound might have a bass component that carries far, while the blade tips produce high frequencies that attenuate quickly. In Wwise, you can create separate attenuation curves for different layers of the same sound by using multiple Attenuation ShareSets and assigning them to different child containers. Alternatively, use the Bus structure to apply different attenuation to frequency bands. Combining volume, LPF, and spread curves yields a richer, more believable spatial presence.

Cone Attenuation for Directional Sounds

For directional sources (megaphones, gunshots, voices), Wwise supports cone attenuation. This adds an angle-based component to the distance curves. You can define a front cone where the sound plays at full volume, and an outer cone where it is reduced and filtered. Customize both the inner and outer angles, and then apply separate distance curves inside and outside the cone. This is invaluable for precise sound localization: a character speaking toward you sounds clear; when you’re behind them, the dialogue is muffled and quiet.

Testing and Integration in Game Engine

Optimizing Performance

While custom curves can be complex, Wwise efficiently caches attenuation calculations. Still, avoid excessive control points – 5–8 points per curve is usually plenty. Use smooth interpolation (Bezier/cubic) instead of linear if you want consistent behavior. Test in the actual game scene with real spatial audio renderers (e.g., Windows Sonic, Dolby Atmos, or Steam Audio) to ensure curves translate correctly across different output formats.

Additionally, consider using Wwise’s Game-Defined Auxiliary Sends alongside attenuation curves to add reverb or environmental reflections for even more realism. For example, a sound that is far away might have more reverb tail, reinforcing the sense of distance.

Common Pitfalls to Avoid

  • Unnatural silent zones: Avoid making the volume curve hit -infinity before the max distance. Instead, let it fade gracefully with an LPF tail.
  • Ignoring game view: In first-person games, the camera and listener are the same; but in third-person, the listener can move independently. Design curves with the player’s perspective in mind.
  • Over-filtering: Too much LPF can cause low-pass aliasing artifacts; keep the rolloff moderate.
  • Neglecting near-field: Many games ignore what happens within 1–2 meters. Adding a slight boost or spread reduction can make nearby sounds more intimate.

Real-World Examples and Resources

To dive deeper, consult the official Audiokinetic Wwise Attenuation Documentation for a full reference on curve types and parameters. For acoustic principles behind distance attenuation, the Acoustical Society of America has useful resources. Another excellent read is the GDC talk “Advanced Game Audio Design Using Wwise” which covers spatialization and attenuation in depth.

Conclusion

Custom Wwise attenuation curves are a cornerstone of professional game audio design. By understanding the physics of sound, leveraging Wwise’s multi-parameter curves, and following a structured design process, you can achieve highly accurate sound localization that enhances immersion and gameplay clarity. The effort invested in crafting volume, filtering, and spread curves pays off in a more believable, engaging audio experience. Experiment with different shapes, test in-engine, and iterate – your players will hear the difference.