This study presents the preparation and property characterisation of biomass aerogels as sound absorption building materials. As innovatively sustainable porous materials, four natural, degradable bio-polymers (gelatine, starch, wheat straw, and konjac glucomannan) were chosen as the raw materials to prepare the environmentally friendly biomass aerogels with sound absorption property, through the efficient freeze drying method combined with a sol-gel process. Results indicated that the four components may have different effects on the aerogel pore structure, and the aerogel formula was thus optimised to reach the best sound absorption, and the sound adsorption mechanism was analysed. Appropriate addition of gelatine and starch components could enhance mechanical properties proved by texture profile analysis, and also possibly contributed to the formation of through-hole structures enhancing sound absorption performance verified by microstructure images of biomass aerogels. The presence of wheat straw may cause pore shape changes of biomass aerogel due to the special multi cavities structure. Konjac glucomannan with high flexibility and linearity may work as the aerogel skeleton material. Within the experimental range, biomass aerogel with the optimised formula had an average sound efficiency 0.352, density 0.047 g/cm3 and porosity 94.46 ± 0.04%. It shows better sound absorption performance than traditional sound absorption cotton (average sound efficiency 0.225). The decomposition temperature of biomass aerogels has been determined to be 282.06 to 354.94°C. These results demonstrate the high sound absorption potential of biomass aerogels for building applications.