powdrhound

Recently my alarm siren had quit working on my 06 Cayenne S. It started when l noticed that I was not getting the chirp upon arming and disarming of the alarm. I actually noticed that I could still hear it very lightly but it eventually fully quit. Has anyone replaced these? My steering wheel horn functions normally so obviously there is a separate horn for the alarm. I looked in PET and it lists both an alarm horn (95563711702) and alarm siren (95561823701). The horn is about $10 while the siren is $140. Do both need to be replaced? Why are there two? Thx!