Sony T99 has a 14.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CCD sensor and features Bionz processor. On the other hand, Canon ELPH 340 HS has a 16.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CMOS sensor and features DIGIC 4+ processor.
Below you can see the T99 and ELPH 340 HS sensor size comparison.
Sony T99 and Canon ELPH 340 HS have the same sensor sizes so they will provide same level of control over the depth of field when used with same focal length and aperture. On the other hand, since Sony T99 has 14% larger pixel area compared to Canon ELPH 340 HS, it has potential to collect more light on pixel level hence have less noise in low light / High ISO images.