adding horn chirp to keyless system

I need to turn a 1 second + pulse into a shorter chirp. I ran into a weird situation maybe some one can help me out. I installed an old Viper Remote start/keyless entry system into a 2009 Toyota Tundra. The problem is that the system does not have a horn honk output wire like the newer systems do. So what I did is diode isolated the + lock and unlock wires through a relay to trigger the negative horn honk wire. This solution worked but the lock/unlock wires pulse for 1 second and the horn is soooo loud its abnoxous. So I need to change a 1 second pulse to a smaller pulse. I thought about using an alarm siren instead of the horn and using a resister to turn the voltage down so it wasn't as loud, but ideally if I could get a chirp sound like the lexus' have, that would be Ideal any suggestions?jake

Any except the first one listed will work for you. 

The third from the bottom is probably the best option for you.

http://www.radioshack.com/search/index.jsp?kwCatid=&kw=piezo%20buzzer&origkw=piezo%20buzzer&sr=1

relay +552 flasher can = horn honk

siren + output   to 85

ground   to   86

12v bat to   87

flasher can input   to 30

flasher can output to Positive horn at horn not before relay

The Radio Shack piezo buzzer worked perfectly, Thanks!jake