I have successfully done the following in my Samsung Galaxy S2 phone. Not checked in other Android phone models. You guys can give a try.
How to Disable Camera Sound in Samsung Galaxy S2
To use this method you need to create an empty file named local.prop and add a line ro.camera.sound.forced = 0 into it.
You can do this in notepad from your computer and simply paste the code given below into it i.e
ro.camera.sound.forced = 0
Now you need to save the file as local.prop and please don't save it as local.prop.txt.
Now simply transfer this file to your galaxy s2 phone to the location <phone>/data/.
Simply reboot your phone put your phone on silent mode and now if you click a picture using your phone there will be no shutter sound to disturb you.
To restore the sound simply delete the file and reboot your phone.