A capacitance-type transducer has a substrate having a cavity, a vibrating electrode plate disposed above the substrate, a back plate disposed on the substrate, a fixed electrode plate disposed on the back plate opposite the vibrating electrode plate, a plurality of holes formed in the back plate and the fixed electrode plate, and a protrusion disposed on the back plate at a location opposing the vibrating electrode plate. In a view from a direction perpendicular to an upper surface of the substrate, a shortest distance from a cross-sectional center of the protrusion to an edge of a hole adjacent to the protrusion is larger than a shortest distance from a center of a region that is surrounded by the holes but not provided with the protrusion to an edge of a hole in the periphery.