HOW TO MUTE CAMERA SOUND OF ANDROID MOBILES
If your ANDROID MOBILE can't show any option for muting the sound then you have one solution.First of all Open the camera application and reduce the sound with physical button provided at the edges of the phones.If this process can't reduce the sound then you can close the camera app and open any music player app or any other application in your mobile.And reduce the sound with physical Buttons.Then open the camera app and check the sound it will reduce the sound.
The main reason behind this is when you reduce sound in camera app it will reduce the sound but not your app sound.System sound is reduces with the above process.
This method is applicable if you have physical buttons(For increasing and reducing the sound) at the edges of the phone.If you have no physical buttons then you must go to Google play app store and search for sufficient app for reducing the sound.