Ultrasound can be used in sol-gel synthesis as a source of energy which may modify the structural and chemical properties of the resulting gels. Pt/SiO2 sonogel catalysts were obtained and characterized by X-ray diffraction and small angle X-ray scattering. It was found that the aging and polymerization mechanisms are altered by ultrasound. The catalysts were then tested in phenylacetylene hydrogenation, showing a high selectivity toward styrene.