Audio - Attenuation/Spatialization

When you set an audio to use Attenuation/Spatialization so it plays louder as the player get closer, that all works.

However I cannot seem to find the answer to the ? what happens to that audio when the player is so far away it cannot be heard.

The sound obviously uses some audio channels to play, but are those channels always assigned to the audio even when it cannot be heard or is the audio switched on when needed

e.g. By default Unreal seems to support 32 channels of audio. So if you have 2 audios that use Attenuation/Spatialization and are stereo (2 channel), then are 4 channels permanently used for the duration of the level, leaving 28 to use elsewhere?