A method and apparatus for stabilizing adjacent vertebrae. Also, this phenomenon gives rise to problems relating to damage of parts, life of a loading motor and the like. Any displacement of each electroactive bending actuator effects displacement of the membrane. The timing of the transmission is determined automatically after the event is received. A first stitch bond is formed on the connection pad, and a second stitch bond is next formed on the connection pad that is contiguous with the first stitch bond. Thus, varieties of sounds become rich and 3-dimensional hearing experiences are enhanced with low cost for a 4-channel earphones system.