You can't adjust the volume level for this sound.
Stop phone from speaking
Some voice commands (like “What's up?” and “What is the current weather?”) cause your
phone to speak in response.
To stop the phone from speaking temporarily, touch
.
To prevent your phone from speaking:
1. Open
the Google app.
2. Touch More > Settings.
3. Touch Voice.
4. Turn off Spoken results.
Turn off charging sounds
If you don’t want your phone to make a sound when it comes in contact with a charger:
1. Go to Settings > Sound > Advanced.
2. Turn off Charging sounds.
Personalize your phone : Sounds 58