Read your handbook under AUDIBLE WARNINGS
Seat belt reminder
In some markets, if the driver's seat belt has not
been fastened when the starter switch is turned
on, a warning chime will sound (one second
frequency). The chime operates in conjunction
with the seat belt warning light and sounds for
6 seconds, or until the seat belt is fastened
(whichever occurs first).
In Gulf States markets, either; the chime will
continue sounding indefinitely until the seat belt
is fastened, or; the chime will sound for 6
seconds whenever the driver's door is opened
and closed with the starter switch turned on.