By default, the horn doesn't sound when you lock/unlock (just a beep). If that's what you're referring to, you need to either go to a dealer or get an OBD-II reader and app to customise the settings. You can check your owner's manual to see what is customisable by you (via the MFD) or what is customisable only by the dealer.
Definitely a horn sound (Beep Beep) not a digital Beep. It does make the digital beep simultaneously with 2 horn beeps while locking and unlocking the doors.
If you bought it used, it's possible the previous owner enabled the horn by modifying it. I looked in the owner's manual and there's no option for horn, just the beep (or buzzer as the term the manual uses).
Yeah, and it's not listed in Carista either, I have it and I checked. You can lower the volume of the beeps in the center screen settings, that's it. Ask your Toyota dealer and as mentioned above, look for aftermarket parts. Maybe under the dash.
