A micro electro-mechanical system (MEMS) acoustic sensor is disclosed. The acoustic sensor comprises a backplate and a diaphragm. The acoustic sensor further comprises a flexible member and optional spacer member disposed between the backplate and the diaphragm resulting in a gap between the backplate and the diaphragm. The gap can vary in response to impinging pressure on the diaphragm based on the design of the flexible member and resulting in a variable capacitance between the backplate and the diaphragm. The change in the gap can result in a change in an electrical characteristic associated with the variable capacitance and can be converted to an electrical output signal corresponding to the impinging pressure on the diaphragm. The flexible member can be part of the backplate or diaphragm.