Recent advancement in controlling noise through sound absorption provides an opportunity to investigate various porous materials including fiber-based composites. Natural-fiber-based composites exhibit relatively good sound absorption capability due to their porous structure. Surface modification by alkali treatment can enhance the sound absorption performance. These materials can be used in buildings and interiors for efficient sound insulation. Natural-fiber-based composites have advantages such as high abrasive resistance, low emission of toxic fumes with heat, high specific strength, light weight, low cost, and eco-friendliness. Very rapid growth has been observed in the innovations and use of natural-fiber-based materials and composites for acoustic applications.