Probably a cooling fan cutting in if the games are CPU-intensive. Take the side off the case and use a sheet of A4 paper rolled into an ear-trumpet shape to identify which one.
Safety notice: take care not to perforate your eardrum.
The Evil Within 2 review-in-progress
InVision Studio takes on Adobe XD and Sketch
Camera tips to take better iPhone photos
Comment transformer un iPhone en borne Wi-Fi ?