SOLUTION Volume of the automations speaking voice too low
Many users complain that the voice of the automations is too low in volume.
The solution is not documented but it works like this: the volume of the voice of the automations is related to the volume of Siri's voice.
You have to adjust the audio volume (up/down keys) while Siri is talking, that volume will then be used next times for the speaking voice of the automations as well.
iPhone 14 Plus, iOS 17