Calculating bits/sample from a digital MEMS microphone
Ten bit data can be increased in resolution if there is gaussian noise present and oversampling is performed. 4 times over sampling increases the resolution from 10 bits to 11 bits. 4 x 4 times oversampling gets you one more bit and 4 x 4 x 4 (=64) times oversampling gets you another bit. So with 64x oversampling you get 13 bits resolution from a 10 bit source.

See this source from silicon labs entitled AN118, IMPROVING ADC RESOLUTION BY OVERSAMPLING AND AVERAGING