PURPOSE: To prepare the titled composition giving a cured product having excellent acoustic effect such as high internal loss, etc., and suitable especially to speaker box, etc., by compounding a thermosetting resin with aromatic polyamide fibers, inorganic filler, and curing agent.

CONSTITUTION: The titled composition (100pts.wt.) is prepared by compounding and kneading (A) 17W40pts.wt. of a thermosetting resin (preferably a polyester resin, etc.), (B) a sufficient amount (50W80pts.wt.) of an inorganic filler having an average particle diameter of 0.2W100μ (e.g. calcium carbonate) to give a specific gravity of the cured resin composition of ≥1.8, (C) 3W15pts.wt. of aromatic polyamide fibers (filaments of 2W20mm length) as fibrous reinforcing material, and (D) a curing agent (e.g. peroxide).