Hundreds of online forums going back more than a decade indicate that there is a lot of confusion about the significance of the stages of locking a car with a remote. With most newer remote locking systems, the first press of the key fob will cause the locks to engage and security to be armed.

With most cars, safe, secure locking can be accomplished by pressing the key fob only once. When you press the key fob twice, the horn or another acoustic alert will sound for psychological assurance, and nothing more.
The confirmation sound is unrelated to security.

Many people assume that the first press of the lock button locks the doors and the second press arms the anti-theft device, and think that the "confirmation" sound is related to the anti-theft system, when it isn't. With most anti-theft systems, going back a quarter of a century, and including pre-factory installed aftermarket car alarms, the anti-theft system arms itself after a brief interval after the door is closed, whether or not one presses the key fob.

If you want to lock your car quietly but can't break the habit of needing some kind of assurance, many cars can be configured to a setting where the lights will flash to indicate that the car is locked. Other quiet options include being close to the car when you lock it and listening for the "clunk" sound of the locks engaging, and trying the door handle after you've locked the car. If your car has an alarm, you can usually see a blinking light on the dashboard that indicates security status.

You should familiarize yourself with the car's owner manual, which will provide guidance about lock confirmation technology. Some manuals are out of date, or are never updated, but have basic information about locking that is somewhat helpful if you know which aspects are out of date. Nissan cars and many Hyundai and Kia models now use an electronic tone for confirmation, but their owner manuals may still refer to a horn - or lights. If there is information about flashing lights, that part is most likely up to date.

You should be able to consult your dealership or a regular mechanic about configuring the technology. If you find dealership or auto body shop technicians unhelpful, you can also search YouTube for a video about configuring your car's lock technology. Some videos are posted by mechanics and other experts who will post a phone number, and we've had luck contacting some people this way where we were not required to pay for advice.

These are good sample videos. Note that in US automotive parlance, "horn honk" is called "horn chirp" but is indeed a horn honk, and we call it a horn honk; a "chirp" is that old fashioned "Whoop! Whoop!" sound you hear in Lifetime movies. The relatively quiet sound Toyota uses we call an electronic tone - and that can be disabled or switched with flashing lights as well.

Dodge
Late model Chevy
Reconfigure VW newer version and older version
Turn off Remote Left in Vehicle alert in a Chevrolet
How to unlock sound of Mercedes-Benz
Horn when locking doors (Mercedes-Benz)
Hyundai Lock Horn - How To Turn It Off

Another place where you can find help disabling or reconfiguring lock confirmation is in tens of thousands of car forums - you should be able to find a decent forum within a few minutes. Some of these involve technical problems that couldn't be resolved at a dealership, and other are from people trying to reconfigure their car's sound for the first time without bringing the car in to be serviced.

An online mechanic service
Somewhat older Jeep Grand Cherokee instructions
Another Chrysler forum
Solutions to the Prius backup beep, a disturbing flaw with a brand that has otherwise been responsible with sound

This passage appears in the 2017 Chevy Impala owner manual, but phrasing like this will or should appear in most current owner manuals:

This vehicle has a passive
theft-deterrent system.

The system does not have to be
manually armed or disarmed.

The vehicle is automatically
immobilized when the key is
removed from the ignition.

The system is automatically
disarmed when the vehicle is
started with the correct key.