Abstract: The invention relates to a sound insulating structure including low-density and high-density layers. The low-density layer has first and second fibrous layers and ranges from 0.5 to 1.5 kg/m.sup.2 in surface density. The first and second fibrous layers are respectively made of first and second thermoplastic synthetic fibers. The first and second fibers respectively have first and second single fiber diameters, each of which diameters is in a range of from 3 to 40 .mu.m, and first and second fiber lengths, each of which lengths is in a range of from 10 to 100 mm. The high-density layer is formed on the low-density layer and is made of an air-impermeable polymer material and has a surface density that is higher than that of the low-density layer and ranges from 1 to 10 kg/m.sup.2. The low-density layer is high in sound-absorption coefficient and at the same time low in spring constant. Therefore, the sound insulating structure becomes substantially improved in sound insulating capability.

Abstract: The disclosure relates to a sound insulating structure formed on an automobile floor panel on which at least one of a vibration and a sound is incident. This structure includes a covering layer for covering the panel and a cushioning layer for reducing an impact of the at least one of the vibration and the sound. This cushioning layer is interposed between the covering layer and the panel and made of a nonwoven fabric. This nonwoven fabric includes 5-95 wt % of a first fiber and 5-95% of a second fiber, wherein the total amount of the first and second fibers is 100 wt %. This first fiber has a fineness within a range from 1.5 to 40 deniers, a first melting point, and a first portion including polyethylene terephthalate. The second fiber has a fineness within a range from 1.5 to 15 deniers, a core portion, and a sheath portion covering the core portion. A majority of the core portion includes polyethylene terephthalate.