Nikon P340 has a 12.0MP 1/1.7" (7.44 x 5.58 mm ) sized BSI-CMOS sensor . On the other hand, Sony HX7V has a 16.0MP 1/2.3" (6.17 x 4.55 mm ) sized BSI-CMOS sensor and features BIONZ processor.
Below you can see the P340 and HX7V sensor size comparison.
As seen above, Nikon P340 has a 1.5x Larger sensor area than Sony HX7V. Larger sensors give photographer more control on the depth of field and blurry background compared to smaller sensor when shot in same focal length and aperture.