Silica aerogel as the lightest solid with very low thermal conductivity and strong sound barrier properties has attracted widespread attention in recent years. Also, different forms of biomass products have been recently applied as sound insulation additive to polyurethane foams. Application of such materials is motivated by their availability, low price and biodegradability. Rigid Polyurethane (PUR) foams are among the most common materials for acoustic applications. Properties of these foams could be easily modified by changing their chemical composition or by adding reinforcement fillers. In this study, different PUR foam samples (ESPAK90 (PUR foam, Prochima, Italy)), containing 3 weight percent (wt.%) of hydrophobic Granular Silica Aerogel (GSA, Cabot, USA) or Powder Silica Aerogel (PSA), 7 or 10 wt.% of Italian pine sawdust (SD) with particle sizes from 0.5 to 4 mm and samples containing both SA and SD were prepared. The acoustic properties of the samples were investigated by measuring their Acoustic Absorption coefficient (Abs) and Transmission Loss (TL) in the frequency range of 250 to 6000 Hz through impedance tube. Measuring acoustic properties revealed that samples with GSA had the highest TL in comparison with all the other samples but not much higher than that of the neat PUR foams which showed high absorption coefficient in the frequency range of 3300-5000 Hz. All samples with silica aerogel or sawdust showed higher absorption coefficient in comparison with PUR foam counterparts. On the other hand, SD samples showed better absorption properties but their TL was lower than that of the neat PUR foams. Generally speaking, the results revealed that GSA could be used as an additive to improve sound barrier characteristics for sound insulating applications. However, when only better sound absorption properties are needed, pine sawdust is a more economical additive for rigid polyurethane foams especially in low humidity or dry climates.