Silica-Aerogel Cotton Composites as Sound Absorber

In the research reported in this paper, silica aerogel was synthesized in a cotton nonwoven mat (CNM) and then the composite was used as a sound absorber. The experimental data indicated that using aerogel as a coating on CNM significantly improved sound absorption up to 2,500 Hz. However for higher frequencies silica aerogel coating reduced sound absorption compared to neat CNM. The best sound absorption performance of the CNM coated aerogel happened between 250 and 2,500 Hz. The effects of different processing conditions were studied on the final properties of the silica aerogel and consequently on the sound absorption of the coated CNM. The pore size and surface area of the synthesized silica aerogel had no direct influence on the sound absorption properties of the composites; on the other hand, the density of the silica aerogel was the only critical factor that determined the sound absorption coefficients of the composites. (C) 2014 American Society of Civil Engineers.