Bent neck has variable structure for hinged ultrasonic detector, and thus different section song necks can be bent to different curvature. In one embodiment, rigid member protrudes into bent neck, sets one section of the inflexion point bent neck in rigid member. In another embodiment, make connecting rod song neck length degree different, until causing different parts that there is the maximum curvature of different radii. Bent neck is packed into sheath which is presented the region of different hardness in another embodiment, and the attachment point of thickness or spacing is to bent neck.
