Xperia Active :: Turn Off The Camera Shutter Sound?

I have an Xperia Active ST17i, android versions 4.0.4, and ever since I bought it I'm trying to find a way to turn off the sound but now luck. I have no option in my camera application. I read on different forums that I need to modify my build.prop file. Can't do that since I can't root my phone. I found the file, I found the line that I need to modify, but can't touch it ofc. I tried factory reset, in the hopes that it would put the camera sound from 1 to 0, but still no luck. I tried to put the phone on silet. Every application is silent, expet for the freakin` camera!!

So how the heck do I turn off that freakin` sound?