How would i get a "rumbler" / "howler" effect for my police sirens?

I dont know if this is the right topic so I apologize if isnt.

Anyways, im trying to get a rumbler effect kinda like as shown in this video. Is there anyway to do this within studio using the sound modification objects? Or would i have to use a external program?

It’s sort of like rapidly moving resonances of high-frequency sine waves. Usually succeeded by low-frequency oscillators.

Any way i can achieve this? Would i have to use a external program to modify the original sirens or could i use a sound modifier in studio to do this.

An external program is required for a good sound. The sound modifiers are not that amazing but you should experiment with them.