I travel a lot, and one of the places I visit frequently is India. As a result, I usually carry SIM cards from the places I spend the most time in. Whenever I insert an Indian SIM card into my phone, the phone camera starts playing a shutter sound whenever I take a picture. This takes place on all apps on my phone that use the camera, from the default camera app to Instagram and Snapchat. This takes place in all phone modes and volume settings, including in airplane mode.
When a US or UK SIM card is inserted, the camera is silent and does not make the same noise when a photo is taken. I have noticed that this takes place with SIM cards of all operators in India, and this seems to have been the case for at least the last 2 years. I believe this is related to some legal requirement in India. The only thing I've found about this is a similar thing happening in Japan, as per this TripAdvisor forum thread.
Does anyone know why inserting an Indian SIM card into a phone activates an impossible to disable camera shutter sound?