The Nooie Cam Doorbell chime be turned either on or off, but the volume cannot be adjusted. The volume of the Base Station can be adjusted. See: How do I adjust the volume of the Base Station?
To turn the Doorbell sound on or off:
Open the Nooie App, tap on Nooie Cam Doorbell
Tap on the Setting icon on the top right
Tap Audio / Video
Next to Doorbell Sound, tap on the toggle to turn the doorbell sound on and off.