Just to provide closure, my issue was also the harness. I ended up buying the new harnesses and soldering them in. Horns work fine now and it's loud as hell. Even louder than when it worked before so it was definitely one of my horns that was bad and causing the fuse to blow.

 

Have you figured out what is the cause of this sound???

Something new is happening though. When I put the key in and turn it, I hear a very faint sound of a horn coming from inside the dash on the driver side. It sounds just like the horn is sounding, but is very quiet. I confirmed it is not the horns themselves sounding, and the sound stops after about 5 seconds. You then have to turn the car off, take the key out and re-insert to and turn it on to get it to do it again. Happens every time. I also need to add that the horns do perform a double beep when setting the alarm. They always have, even when the fuse was blown.

 

Just thought of something:

Is it possibly the tone you get when you forget and leave your headlights on? Try leaving the headlights on and open the driver door to see if it gets louder. Then turn it off and try again....

 

Very strange thing, we turned the lights off (normally in Auto). It did not make the noise for all of our driving, about 80 miles total and 3 hours later, including about 7 stops in between. Then it happened again, but only once and it happened when we were approaching and stopping at a crosswalk. Could it be some other type of warning sound??

 

7 stops in 80 mi is a lot of on and off. Have you verified battery health?