In India, the sound of camera’s shutter is permanently ON because of Google’s original design, even if you’ve switched off the shutter sound in camera settings. However, we will change this option so users are able to normally turn on/off camera shutter sound in the future update.
Because of local government regulations, if you purchased your phone in either Japan or South Korea, the Camera sound option is not shown on Camera settings and the shutter sound will be ON even if you use your device in other countries.
To check if your phone was purchased in Japan, you can look for the ROM type of your device by doing the following:
Go to Settings, then tap About.
Look for the country code in Software information.