@rameckmd- I believe that whether or not your phone makes a sound when
it receives a notification is based entirely on your phone's sound
settings for notifications. It is outside the scope of control of the
Nest doorbell.
The internal battery on 1st generation died after a few years causing
the doorbell to power off and reboot upon pressing the button. I was
told that I would need to buy a new doorbell. I repeat: no option to
replace a $5 battery, but must repurchase ...