iPhone 5's rear camera will feature a larger f/2.2 aperture than iPhone 4S's f/2.4. However, larger aperture means more noises
Wrong. A larger aperture (f/2.2 is larger than f/2.4) means LESS noise, since more light is hitting the sensor through the larger hole (aperture). The larger the aperture, the smaller the f/ number. A larger f number would mean more noise, and would mean a smaller aperture, which is apparently not the case.