Abstract: Honeycomb structures, glass fiber mats, and polyurethane on both sides with respect to a perforated plate. A sound absorption hole is formed in at least one of the glass fiber mat and the polyurethane arranged on both sides of the honeycomb structure and passes through each cell, so that sound absorption performance in a high frequency band as well as a low frequency band can be improved using multilayer sound absorption characteristics. Noise passing through the honeycomb structure is changed to noise to be absorbed. Since the diameters of the sound absorption holes formed to pass through the honeycomb structures arranged on both sides of the perforated plate are different, a sound absorption band of a desired frequency may be easily adjusted. The sound absorption performance in a low frequency band of 1,000 Hz and a high frequency band of 5,000 Hz or higher can be improved.

Abstract: A method of manufacturing insulation where carbon nanotubes are added to a polyurethane foam sheet widely used as an insulation substrate, where the cell structure of the foamed polyurethane foam is changed. Accordingly, the NVH performance in a middle and high frequency band of 1,000 Hz or more may be improved while minimizing an increase in weight (lighter than resin felt or glass wool). In particular, since at least one air layer is molded between two polyurethane foam sheets, noise passes through the at least one air layer in the middle of the polyurethane foam sheets when passing through the polyurethane foam sheets, where noise reduction performance may be further improved. In addition, since a mesh made of jute, along with the at least one air layer, is additionally provided between the two polyurethane foam sheets, the sound absorption performance of an insulation may be further improved.

Abstract: A load floor for a vehicle, by which, as the load floor is manufactured by including manufacturing a honeycomb structure with paper and adding polyurethane sheets to both side surfaces of the honeycomb structure, light and sufficient structural stiffness and a sound absorption effect are obtained through the honeycomb structure. As the polyurethane sheets are respectively provided on both surfaces of the honeycomb structure, sound absorption and insulation performances are obtained to further increase a sound absorption and insulation effect.

Abstract: A load floor for a vehicle, by which, as the load floor is manufactured by including manufacturing a honeycomb structure with paper and adding polyurethane sheets to both side surfaces of the honeycomb structure, light and sufficient structural stiffness and a sound absorption effect are obtained through the honeycomb structure. As the polyurethane sheets are respectively provided on both surfaces of the honeycomb structure, sound absorption and insulation performances are obtained to further increase a sound absorption and insulation effect.