Summary form only given. With a reflective grating, the laser modes can be partitioned and noise level will be enhanced. This generic noise-enhanced feature is named as mode partition noise, which has a quantum mechanical origin, in which the noise level of modal output is larger than that of total output. Here, we report a unique manifestation caused by the interplay between noise and chaos in a free-running multimode Nd:YVO/sub 4/ microchip laser, mainly, as chaos appears, mode partition noise could be smaller than total output noise.