Siri responses, voiced or silent

Siri is inconsistent about either completing an action with a voice confirmation, or completing the action silently. Most of the time I’d prefer a voiced response, but occasionally I’d prefer a silent confirmation. Sometimes I WANT a voiced response, but only get a screen display, no sound. How to control audible responses? I wish I could just say, “Do ACTION silently.”

And then there are the times when Siri just doesn’t wake up at all. “Hey Siri, do ACTION…” and nothing happens. Repeatedly.