Nonlinear elastography systems and methods are provided. The database tables are stored within a database file that contains an index structure to assist in the determination of the location of the table within the file. Also, it is possible to keep the distance between the substrate and the first porous member, with a simple construction. Because the fabric strap itself is provided with a cushion composed of erect fine hairs, it has a softer feel when in contact with skin and relieves the pressure feel generated by the wire within the underwear on skin. With the second stage filter, it is possible to further suppress noise in low SNR conditions without affecting the overall filtering response time. With this, a droplet that sticks to the water-leading groove disposed on the outer surface of the bottom wall is brought into contact with a droplet that sticks to the tip of the cut-out portion disposed on an inner surface of the bottom wall to flow out a droplet that sticks to a peripheral edge of the drainage port to the outer surface of the bottom wall.