The present disclosure includes: a vibrating plate having a piezoelectric body connected to a main surface thereof; a cover including a top plate that faces another main surface of the vibrating plate and that has an opening part, and a side wall connected to an outer peripheral portion of the top plate so as to surround a space between the top plate and the vibrating plate; a support portion connected to the side wall and supports an outer periphery of the vibrating plate; an opening between the side wall and the vibrating plate; and a protrusion on any one out of the top plate, the side wall, and the vibrating plate so as to protrude into the space. The protrusion is provided between the opening part of the top plate and the side wall in a cross section.