ing in detail a preferred embodiment thereof with reference to the attached drawings in which:FIGS. 1A and 2A are an exploded perspective view and a plan view, respectively, showing a hard disk drive adopting a conventional filtering apparatus;FIGS. 1B and 2B are sectional views showing a part of each of FIGS. 1A and 2A, respectively;FIG. 3A is an exploded perspective view showing a filtering appa