Periodic behaviors in a piezoelectric line ink jet printhead are studied. The printhead is composed of a monolithic structure having resolution of 600dpi in 4.25 inch effective print width. The structure is made up of plural metal foil layers, in which parts of channels are formed respectively, and actuator units mounted on top of them. The nozzles opened in the bottom layer are lead from cavities underneath of the actuator units through a descendant conduit named descender. Analyses on experiments suggest that a descender, cavity and unimorph actuator could make an individual acoustic element, of which acoustic period is much shorter than that oft the discharging unit.