A sensor includes a substrate; and a corrugated diaphragm offset from the substrate. The corrugated diaphragm is configured to deflect responsive to a sound wave impinging on the corrugated diaphragm. A cavity is defined between the corrugated diaphragm and the substrate, the corrugated diaphragm forming a top surface of the cavity and the substrate forming a bottom surface of the cavity. A pressure in the cavity is lower than a pressure outside of the cavity.