This is a siren pack I created using multiple sirens as you can hear in the video. I will admit, it's not perfect and will be updated from time to time but replaces most in-game siren tones with decent ones. Feel free to comment with suggestions, etc.

https://www.youtube.com/watch?v=NZIW39oH82o

Make sure you backup any files that you wish to keep and not have overwritten.