I did a quick search and found them. I added them to the audio file name section.
Here is a link:
Its under car sounds
And as for now you cannot use air horn together with normal sirens sadly. But you could mod it!!
At this stage of modding it is NOT possible to make such lightbar, or even change light bars. But you can edit light bars by mesh files. But they will most likely break or look
Herogus3xD's post in MODS was marked as the answer
You need to get Unity assets bundle extractor. From there just check out my tutorials or other guides to get into FL modding!
It is recommended that you join the Flashing Lights discord server! https://discord.gg/flashinglights
Bunch of youtube tutorials can be found here:
Flashing Lights: How to replace a character skin! + Full explained! https://youtu.be/0iMt3W4_9fM
Flashing Lights: How to import a map skin! https://youtu.be/MfFr80E1yAo
Flashing Lights: How to change sirens https://youtu.be/I68Lpchhto0
Flashing Lights: How to replace the PD explorer texture! https://youtu.be/U4MrTguvckc
Flashing Lights: How to replace the PD CVPI texture! https://youtu.be/zhyCx3YNhrA