Because the foam separator has deteriorated. Remove three screws from back side of horn, remove honk button and separate. you can the figure out what new material to use to replace the bad foam.
It is important to know where the parts are within a car. The horn relay in a 1993 Mazda Protege is found in the cars fuse box.
I have a 1993 Mazda Protege LX and I was told that there is no relay for the horn, there is a horn switch inside your steering wheel. that might help
in the stearing wheel
behind the plastic grill on the front.
The horn fuse is the same as the stop lamp fuse
Your horn is in back of the radiator grill (Grill in front of the car)
The horn for the 1990 Mazda Protege is located near the right turn signal at the front of the car. To the left of the radiator when your looking at the engine with the hood up.
The fuse for the horn should be on the drivers side underneath the dash. There is a diagram on it that shows the horn fuse.
It is in front of the radiator and the horn itself can be bad.
Have your Mazda dealer parts department print out a picture of the relays location for you. They will do this if you ask them.
Open hood and disconnect the wire from the horn itself located under right front fender.
horns are usually located near the grill area in front of the car.