OK its done now, i went through all the 52 sounds and checked their ranges one by one inside gta2 by moving my character until the sound was heard. they are pretty accurate now, only thing that makes them inaccurate is that the spheres rendering is blocky:

easy to spot sound range bugs, there should be two sound sources here!

how far will the alarm be heard? pretty far.
i might fix the biggest spheres to render with better resolution... and the spheres colors kinda looks ugly too. but at least its useful since you see the area easily where the sound is played because it renders it whiter than the area where its not heard.
note: the spheres will be displayed only when you select the sound objects.