I got some good news and some bad news. 

Bad News: I had to scrap the PA20A siren mod because I was still unable to find a higher quality siren sound for me to sample. 

Good News:

https://www.youtube.com/watch?v=NUgAd49x5fs 

 

This right here is the PA15-CPA25 old school siren used in police cars in the 60's-70's and I not only have managed to sample a much more higher quality sound for the wail and yelp but it works fairly well in GTA 5. Plus this was less of a hassle to work with in AVS Audio Editor and Audacity. <3

I've lowered the pitch of the wail and yelp to match the sound of the PA20A but I've greatly increased the tempo of the SIREN_2 audio file and made another copy of this modded yelp as POLICE_WARNING. 

Do keep this in mind however. There are reports that certain audio archives have been muted in game regardless of rather the sound mods were installed properly or not. To ensure that the audio archives for vehicles won't be muted in game make sure that the vehicle.oac file or the vehicle.awc file doesn't exceed over 15.7 MB (at least under or around 15.75 MB not over it) in size (you can check the size of the vehicle.awc file in OpenIV under RESIDENT.rpf) and make sure that the siren sound audio files have the appropriate bitrate/sample-rate/etc (32000hz, 16bit mono, 512kbps) for the vehicles.awc file.

I don't think there's much to fix or re-work on at the moment. However if the modded police sirens in-game are somewhat quiet or not loud enough compared to other sirens, I'll try to increase the volume by amplifying it on audacity. I will upload a preview video soon. =)

Federal Signal PA15-CPA25 Siren Mod - WIP.rar

I got some good news and some bad news. 

Bad News: I had to scrap the PA20A siren mod because I was still unable to find a higher quality siren sound for me to sample. 

Good News:

https://www.youtube.com/watch?v=NUgAd49x5fs 

 

This right here is the PA15-CPA25 old school siren used in police cars in the 60's-70's and I not only have managed to sample a much more higher quality sound for the wail and yelp but it works fairly well in GTA 5. Plus this was less of a hassle to work with in AVS Audio Editor and Audacity. <3

I've lowered the pitch of the wail and yelp to match the sound of the PA20A but I've greatly increased the tempo of the SIREN_2 audio file and made another copy of this modded yelp as POLICE_WARNING. 

Do keep this in mind however. There are reports that certain audio archives have been muted in game regardless of rather the sound mods were installed properly or not. To ensure that the audio archives for vehicles won't be muted in game make sure that the vehicle.oac file or the vehicle.awc file doesn't exceed over 15.7 MB (at least under or around 15.75 MB not over it) in size (you can check the size of the vehicle.awc file in OpenIV under RESIDENT.rpf) and make sure that the siren sound audio files have the appropriate bitrate/sample-rate/etc (32000hz, 16bit mono, 512kbps) for the vehicles.awc file.

I don't think there's much to fix or re-work on at the moment. However if the modded police sirens in-game are somewhat quiet or not loud enough compared to other sirens, I'll try to increase the volume by amplifying it on audacity. I will upload a preview video soon. =)

Federal Signal PA15-CPA25 Siren Mod - WIP.rar

Here's the preview of this siren mod:
https://www.youtube.com/watch?v=87Skd_EqUSw 

http://www.lcpdfr.com/files/file/8462-federal-signal-pa-15a-siren-police-version/