OpenAL Distance Model AL_MAX_DISTANCE Gain Behavior

Distance Attenuation Configuration

OpenAL 1.1 provides several distance models via alDistanceModel to control how sound gain decreases as a source moves away from the listener. The AL_MAX_DISTANCE parameter is intended to define the limit of this attenuation effect, but its impact on audibility varies based on the selected model.

Clamping and Gain Cutoffs

When using clamped models, the distance used in the gain calculation is restricted to the range between AL_REFERENCE_DISTANCE and AL_MAX_DISTANCE. However, the resulting gain at the maximum distance is not uniform across models:

• AL_LINEAR_DISTANCE_CLAMPED typically results in zero gain at the maximum distance, effectively silencing the source.
• AL_INVERSE_DISTANCE_CLAMPED and AL_EXPONENT_DISTANCE_CLAMPED may still yield a non-zero gain value when the distance reaches or exceeds the maximum limit.

This creates uncertainty for applications requiring a hard cutoff for distant audio sources to optimize voice counts or maintain atmospheric silence.

Does the OpenAL specification mandate that sources become completely silent beyond AL_MAX_DISTANCE regardless of the model, or is a manual gain gate required for non-linear clamped models? How does this behavior differ between OpenAL Soft and hardware-specific implementations?