Mesures de vitesses acoustiques dans les aérogels de silice

Abstract
The use of silica aerogels as a quarter wave layer for impedance matching of air acoustical transducers has been pointed by FRICKE and AL. in 1986. Their recent published results in 1992 proves the ability and the interest of this approach. Following the same idea, if one want to built efficient transducers, one need precise mesurements of the acoustical properties of a great number of silica aerogel samples. We have choosen a systematical way to verify their properties and find pregnant materials to obtain a good impedance matching in the low ultrasonic range ( 20 kHz - 300 kHz ) between piezoelectric material and air. Mesured acoustical impedance and sound velocity of a wide range of silica aerogel will be presented as preliminar results.