Fix: Unreal SoundCue Not Spatializing in 3D

Footstep cue plays at full volume from both speakers regardless of where the player walks. The wave file is fine, the cue plays at the right times, but the 3D position doesn’t come through. Three settings must align.

The Symptom

SoundCue plays in PIE but the audio is flat stereo: same volume left and right, no falloff with distance, no panning when the player rotates. Sounds correct in the wave editor preview but not in-game.

What Causes This

Unreal’s audio engine spatializes only mono streams. A stereo wave carries L/R channels that already encode positional information; the spatializer cannot meaningfully reposition those. Even with everything else configured correctly, a stereo source wave plays flat.

Spatialization also requires an Attenuation asset on the SoundCue. Without one, the cue is “2D” and the audio engine doesn’t apply distance falloff or panning.

The Fix

Step 1: Make the wave mono. Open the SoundWave asset (the .uasset wrapping the .wav). In Details, find Sound Group Sound → Force Mono. Tick it. The wave is now downmixed to mono on import.

Or reimport from a mono source — preferred for new content because the downmix is lossy and you keep more headroom by authoring mono.

Step 2: Create an Attenuation asset. Right-click in Content Browser → Audio → Sound Attenuation. Name it (e.g. SA_Footsteps).

Attenuation (Volume): true
Attenuation Function: Inverse
Falloff Distance:     3000      // 30 m
Min Radius:           100       // 1 m of full volume
Spatialization:       Panning  // or Binaural for headphones
Air Absorption:       true

Step 3: Assign the Attenuation to the cue. Open the SoundCue. In Details → Attenuation → Override Attenuation, tick it and assign your asset. (Or assign at play time via the function call.)

Step 4: Play at a location.

// In Blueprint or C++
UGameplayStatics::PlaySoundAtLocation(
    this,
    FootstepCue,
    GetActorLocation(),
    FRotator::ZeroRotator,
    1.0f, 1.0f, 0.0f,
    AttenuationSettings   // optional override
);

PlaySound2D bypasses 3D entirely. UGameplayStatics has both; pick PlaySoundAtLocation.

Verifying

In PIE, console: au.3dVisualize.Attenuation 1. Spheres appear around active spatialized sources showing inner and outer falloff radii. Walk into and out of the sphere; volume should change. If no spheres appear, your sound is being played 2D.

Listener Position

Spatialization is computed relative to the audio listener. By default this is the active player camera. If you have a separate listener actor (cinematic), check that the AudioListener is attached to the right camera; otherwise distances are computed from the wrong reference and panning sounds reversed.

Understanding the issue

This bug class falls into a pattern that's worth understanding beyond the specific case. In Unreal Engine, the underlying behavior is shaped by how the engine layers its abstractions - the public API you call, the runtime systems that respond, and the platform-specific implementations underneath. A bug at any layer can produce symptoms that look like they originate at a different layer. Triaging effectively means recognizing which layer the symptom belongs to, even when the gameplay code is what's visible.

The specific bug described above is the kind that surfaces during integration rather than unit testing. It depends on a combination of factors: the asset configuration, the runtime state, the platform's specific behavior. In isolation, each piece looks correct; in combination, the bug emerges. This is why thorough integration testing - playing the actual game in realistic conditions - catches things that automated tests miss.

Why this happens

The triage path for this kind of bug is long. The symptom appears in gameplay, but the cause is in a different system. The reporter describes the gameplay effect; the engineer has to translate that into a hypothesis about the underlying cause. Misdirection is common.

At the engine level, the behavior comes from a deliberate design decision in Unreal. The engine team chose a particular trade-off - usually performance versus convenience, or generality versus specificity - and that trade-off has consequences when you push against it. Understanding the trade-off is what turns 'this bug is mysterious' into 'this bug is the expected consequence of this design'.

Verifying the fix

After applying the fix, the verification step has three parts: confirm the original repro is resolved, confirm no obvious regressions in adjacent functionality, and (for shipping titles) deploy to a small player cohort first and watch the crash and report rates. Each step catches something the others miss.

Reproducibility is the prerequisite for verification. If you can't reliably reproduce the bug pre-fix, you can't reliably verify it post-fix. Spend time getting a clean reproduction before you write any fix code. The fix is fast once you understand the reproduction; the reproduction is the slow part.

Variations to watch for

Related bug classes often share the same root cause. If you find yourself fixing this issue, look for cousins: similar symptoms in adjacent systems, the same data flow but a different value, or the same fix pattern in another module. The catalog of 'we've seen this before' becomes valuable institutional knowledge.

Adjacent bugs often share a root cause. After fixing the case you've found, spend an hour searching the codebase for similar patterns. What's the same call with different arguments? The same data flow with a different entity type? The same lifecycle issue in a sibling system? Each match is a candidate for the same fix, or a related fix that prevents future bugs of the same class.

In production

For shipping titles with a long support window, watch for this issue resurfacing after dependency updates. Engine upgrades, driver updates, OS releases - each one can resurface a bug class you thought you'd fixed because the underlying behavior changed slightly. Regression tests catch the obvious ones; player reports catch the rest.

When triaging a similar issue in production, prioritize gathering data over hypothesizing causes. A player report describes a symptom; what you need is a build SHA, a session timestamp, and ideally a screen recording or session replay. With those, the bug becomes tractable. Without them, you're guessing at hypothetical reproductions that may not match what the player actually hit.

Performance considerations

Performance implications matter when this bug class scales with player count or asset count. A bug that fires once per session is annoying; a bug that fires once per frame compounds. After fixing, profile the affected code path under realistic load. The fix that's correct for one entity may be too slow for ten thousand.

Diagnostic approach

Before applying any fix, gather enough context to be confident you're addressing the actual cause and not a similar-looking symptom. The cheapest diagnostic step is reproducing the bug deterministically - if you can't get the same failure twice in a row, your fix attempts will be hard to evaluate. Lock down the reproduction first.

For Unreal-specific diagnostics, the editor's profiler is the canonical starting point. Capture a representative frame with the symptom present; compare against a frame without the symptom; the diff often points directly at the cause. If the symptom is non-deterministic, capture multiple frames and look for the pattern - the cause is usually a state transition or a specific input value rather than a continuous effect.

Tooling and ecosystem

Modern engine versions ship better tooling for this kind of issue than older versions. If you're on an older release, the diagnostic step may take significantly longer because the tools you'd want don't exist yet. Sometimes the right answer is upgrading rather than fighting through limited tooling.

Within Unreal, the relevant diagnostic surfaces include the standard frame debugger, memory profiler, and engine-specific debug overlays. Each one shows a different facet of what's happening. The frame debugger reveals draw call ordering and state transitions; the memory profiler shows allocation patterns; the debug overlay reveals per-system state. Bugs that resist one tool usually surrender to another - the trick is knowing which tool to reach for first.

Edge cases and pitfalls

Edge cases for this class of issue often involve specific timing: the first frame after a state change, the last frame before a transition, frames where multiple subsystems update simultaneously. Reproducing these reliably is part of what makes the bug class hard to test.

When writing a regression test for this fix, focus on the boundary conditions that surfaced the original bug. Tests that exercise the happy path catch obvious regressions; tests that exercise the boundary catch the subtler regressions that look like new bugs but are really the original returning. The latter are the tests that earn their keep over the long life of the project.

Team communication

When this bug class affects multiple teams (often the case for cross-system issues), early communication prevents duplicate work. The team that owns the symptom may not own the cause. A 15-minute conversation at the start of triage often saves hours of independent investigation.

If this fix touches a system several engineers work in, a short writeup in the team's engineering channel helps. Not a full design doc - a paragraph explaining what was wrong, what's fixed, and what to watch for. Future engineers encountering similar symptoms will search for the fix; making it findable is a small investment that pays back later.

“Mono wave. Attenuation asset. PlaySoundAtLocation. The audio finds its place in space.”

Related Issues

For sound stuttering, see audio underrun. For occlusion not working, see occlusion.

Mono. Attenuation. AtLocation. The mix opens up.