One problem related to horn assembly has been reported for the 2006 Hyundai Sonata. The most recently reported issues are listed below. Please also check out the statistics and reliability analysis of the 2006 Hyundai Sonata based on all problems reported for the 2006 Sonata.
Low note horn failed at 94k miles. High note horn works, but is much less easily heard. The low note horn was also replaced under warranty on my mother's car, same year/make/model, at about 32k miles.