Keep UI Audio Centered with OpenAL Listener-Relative Sources

The problem: your menu click pans away when the player turns

You have a 3D scene with footsteps, gunfire, and ambient wind positioned in world space. You also have UI sounds: a menu click, a narration line, an inventory open cue. If you place those UI sounds at fixed world coordinates, they pan left or right as the player rotates the camera. A click that should feel like it comes from the interface instead sounds like it belongs to a crate on the far side of the room.

The takeaway: set AL_SOURCE_RELATIVE for UI, leave world audio alone

OpenAL 1.1 defines AL_SOURCE_RELATIVE. When set to AL_TRUE, a source's position, velocity, and direction are interpreted relative to the current listener instead of absolute world coordinates. A relative source at the origin stays head-locked: it remains audible and centered as the listener moves and rotates. World-positioned sources (AL_FALSE) use absolute coordinates and respond to the active distance model, which is what you want for footsteps and environmental objects.

How listener-relative sources behave

A listener-relative source does not track a game entity. It is fixed to the listener at the moment you place it. If you put it at (0, 0, 0), it stays at the listener's position. If you rotate the listener, the source rotates with the camera. That makes it suitable for UI clicks, menu narration, and voice cues that should remain audible and centered as the player moves through a scene. It is not suitable for a companion character's voice unless you update the source's relative position every frame to follow that character.

Worked example: compile, configure, and verify a head-locked UI source

Run these in a C build environment with OpenAL or OpenAL Soft installed. No special permissions are required. Replace audio_check.c with your source file name.

# Compile and link against OpenAL.
gcc -o audio_check audio_check.c -lopenal

Expected check: the compiler produces an audio_check binary with no unresolved OpenAL symbols. Risk: a missing OpenAL development package or wrong library path causes link failure.

Replace ALuint uiSource with a source you have already generated with alGenSources. This assumes an OpenAL context is already current.

#include <AL/al.h>
#include <AL/alc.h>
#include <stdio.h>

ALboolean enableListenerRelative(ALuint uiSource) {
    alSourcei(uiSource, AL_SOURCE_RELATIVE, AL_TRUE);
    ALenum err = alGetError();
    if (err != AL_NO_ERROR) {
        fprintf(stderr, "Failed to set AL_SOURCE_RELATIVE: 0x%x\n", err);
        return AL_FALSE;
    }

    ALint stored = AL_FALSE;
    alGetSourcei(uiSource, AL_SOURCE_RELATIVE, &stored);
    if (stored != AL_TRUE) {
        fprintf(stderr, "AL_SOURCE_RELATIVE was not stored as AL_TRUE\n");
        return AL_FALSE;
    }

    alSource3f(uiSource, AL_POSITION, 0.0f, 0.0f, 0.0f);
    return alGetError() == AL_NO_ERROR;
}

Expected checks:

• alGetError returns AL_NO_ERROR after alSourcei.
• alGetSourcei returns AL_TRUE, confirming the implementation accepted and stored the property.
• At runtime, rotate the listener and confirm the UI sound stays centered instead of panning.

Risk: if you set AL_POSITION to something other than the origin, the sound remains relative to the listener but is offset from it. That can be useful for a fixed headphone-style effect, but it is not a world-anchored object.

Mixing relative and world-positioned sources in one context

A single OpenAL context can mix both modes. Use AL_SOURCE_RELATIVE AL_TRUE for UI cues and AL_FALSE for anything that exists in the scene. World-positioned sources are subject to the active distance model, so moving the listener toward or away from them changes attenuation. Relative sources still respond to listener gain, pitch, and orientation, but they do not pan with world movement.

Source type	AL_SOURCE_RELATIVE	Best for	Behavior when listener moves
UI / menu cue	AL_TRUE	Button clicks, narration, voice cues	Stays head-locked and centered
Footstep	AL_FALSE	Player footsteps on terrain	Pans and attenuates by world distance
Ambient object	AL_FALSE	Wind chime, campfire, machinery	Stays fixed in world space

Limitation: head-locked audio can feel unnatural

Because a relative source rotates with the camera, frequent listener rotation can make the sound feel locked to the player's head rather than anchored in the world. That is usually correct for UI, but it can be distracting for diegetic dialogue. OpenAL is also largely in maintenance mode. For new projects that need HRTF, ambisonics, or active development, evaluate OpenAL Soft or a modern spatial audio engine.

Practical check before shipping

Build a minimal program with two sources. Set one to AL_TRUE at the origin and one to AL_FALSE at a fixed coordinate. Rotate the listener, then move the listener toward and away from the world source. Verify the UI source stays centered while the world source attenuates. Query alGetError after each configuration call. If the relative source pans with the listener, the implementation or context state may not support the property as expected.

Closing

Use AL_SOURCE_RELATIVE as a boundary between interface and simulation. Lock UI sounds to the listener so they survive camera movement, and keep environmental audio in world space so it reacts to player position. Verify with alGetSourcei at startup and a listener-rotation check at runtime.