I have always been annoyed with BlackBerry forcing the BlackBerry cameras to make a noise. I have not seen an actual camera in years that does not allow you to turn this sound off but cellphone vendors seem to think otherwise. Either way S4BB has stepped in on BlackBerry 10 to create Silent Foto Free which allows you to take simple pictures silently. It does not have half as many options as the native camera app but it does work well and is totally silent. Your only real option is to turn the flash on and off and possibly move focus. There is also in app payment support to remove the small ads.
Check out Silent Foto Free in BlackBerry World