Car alarm needs to de-activated.
Old age. Wear. Abuse.
It is because the horn relay is going bad. Mine finally went, now I have to find out how to replace it.
It may or may not.
You failed to mention the car make and modle. If it has a driver's side air bag then the clock spring is possibily bad.
While fuel pumps can go bad with age, a common failure cause is letting the car run out of gas. The pump can go bad in just a few minutes if there is no gas flowing through it.
To wire up a car horn with a button you first need to run one of the wires from the horn to the battery. Take 1of the wires from the horn and run it to where you want the button to go. Connect the wire to the button and that's it.
The hub bearing can go bad and create noise.
The horn goes off by itself on a 1998 Malibu as part of the security system. When the security system is enabled, noises and people touching the car can make the horn go off on its own.
Thermocycling.
The horn is located low on the passenger side, under the right headlight, where it is subject to road slush. After checking fuses, I'd check for corrosion at the terminal on the horn. If the airbag light is on and the horn doesn't work then you have a bad clock spring. That is best repaired by a certified technician.
I would suspect you have a loose or bad ground connection.