Lexus 2003 LS Owner's Manual page 29

Adjusting beep volume
11L165
You can adjust the volume of the beeps which confirm the
locking or unlocking the doors or remind you when the
doors are not completely closed.
Turn the knob counterclockwise to increase the volume or
clockwise to decrease it. The beep sound is completely
deactivated when you turn the knob clockwise until you hear
a click.
Unlocking the trunk lid
11L043g
When you keep the button pushed for about 1 second, you
can unlock the trunk lid.* One beep sounds.
This function does not work when the ignition switch is in the
"ON" position.
NOTE: *The operation method can be changed. Ask your
Lexus dealer for details.
KEYS AND DOORS
15