Acoustic spectroscopy of aerogel precursors
We investigate the acoustical properties of silica gels, which are precursors in the aerogel production process. These gels exhibit a strong “ringing gel” behavior, that is they emit a characteristic sound if one knocks against the container. We study this sound emission with a very simple spectroscopic technique and observe resonances which are characteristic for natural frequencies of a cylindrical body. From a fit of the experimental frequency positions to calculated values, we determine a sound velocity of c T = 4 m/s for a gel sample with porosity φ = 97.5%. This low sound velocity can only be interpreted as the transverse sound mode predicted by Biot’s theory for sound propagation in porous media.
Key wordsAcoustic properties Porous materials Silica gels Aerogels
Unable to display preview. Download preview PDF.
- 7.Landau LD, Lifshitz EM (1991) Lehrbuch der Theoretischen Physik, Band VI: Hydrodynamik. Academie-Verlag, BerlinGoogle Scholar
- 8.Wood AW (1941) A Textbook of sound. Macmillan, New YorkGoogle Scholar
- 10.Abramowitz M, Stegun IA (1972) Handbook of mathematical functions. Dover, New YorkGoogle Scholar