You cannot. However, you can avoid ever hearing "uh huh" if you don't leave a pause between "Hey, Siri." and your request. Just say "Hey, Siri, what time is it?" all in one go.
1. Go to Settings > Sounds & Haptics. 2. To set the volume for all sounds, drag the slider below Ringtone and Alert Volume. 3. To set the tones and vibration patterns for sounds, tap a sound type, such as ringtone or text tone. 4. Do any of the following: Choose a tone (scroll to see them all). siri reponse settings changed in ios 16. Siri response settings once allowed a choice between "Always", "Only when silent mode is off", and "Only with 'Hey Siri'". Settings in ios 16 are "Automatic" and "Prefer spoken response". Automatic doesn't recognize that when Do Not Disturb is on, I don't want a voice response when I use the side button.Then ask Siri a question or to do something. If your vehicle supports "Hey Siri", say "Hey Siri". Then ask Siri a question or to do something. Go to Settings > Siri & Search and make sure Listen for "Hey Siri" is turned on. Siri will also make suggestions in CarPlay about what you may want to do next, such as drive to your next meeting.