An absorbent structure is constructed of hydrophilic fibers and superabsorbent material and has a permeability as determined by an Absorbent Structure Permeability Test and a normalized retention capacity as determined by a Retention Capacity Test. The sampling repletion period of the AD converter is set equal to the pulse oscillation repetition period of the light source or an integer times thereof, and the sampling is synchronized with oscillation of the light source. Moreover, a primary plate is installed within the open end of the bobbin. The additional signal is then recorded in the free area instead of being inserted into the point of insertion. The adaptation of this basic set of models to the speaker is effected in the model space by means of a MAP method in which an asymmetric distribution in the model space is selected as an a priori distribution for the MAP method. A strut mount 10 has a fixing surface portion 18 vertical to a rod 5, an inner member 12 having an aperture 20 provided at the fixing surface portion 18 to which a tip of the rod 5 is inserted from the below, an outer member 14 surrounding an outer periphery of the inner member 12 and mounted on a vehicular body 3, and an elastic member 16 uniting together the both.