I created the Sound Class Master and Sound Mix Master classes, defined them in the project settings, overridden them in the audio_cue and audio asset.
Using a slider I set the volume of the master sound to 0.25, but every time I call the Spawn Sound Cue event, the audio plays the sound with volume 1 and after about 0.5 seconds the volume smoothly adjusts to 0.25.
Basically the volume initially defined in the Master Sound Class controls the volume of each audio latently only after the sound starts.