I haven't seen many issues with this year. Previous models used a separate
alarm siren in addition to the horn. Most horn inop problems on previous
models have been the horns themselves. The easiest way to check is to
install a test lamp in the horn connector under the hood. If the lamp
lights when you press the horn button, the problem is the horn itself.

Have you needed to jumpt start the car or replace the battery recently? I
am currently working on a '04 Elantra car with a blown main 120A fuse,
which will cause the horn to not work (as well as other things such as the
battery to not charge). This will happen if the jumper cables are hooked
up backward or if the battery is installed backward.