Welcome to iPhoneForums, emsicool!
Did you use the side switch next to the volume buttons to mute your device?
If you didn't, toggle it to the side where you see the coloured area (orange or red) below it and try taking a picture once more.
If you did, make sure there's no dirt. Clean the area around the side switch. Also make sure case or protective film don't interfere with the button.