Ceramic-reinforced ceramic matrix composites are being developed for high temperature, high strength applications such as heat engine components, heat exchangers, and recuperators.[1] The particular material considered here is a SiC-fiber-reinforced SiC matrix composite formed by chemical vapor infiltration (CVI). The initial focus was on porosity, which has been linked to the material strength.[1] Ultrasonic attenuation and velocity were investigated since they were expected to be affected by the porosity in the material.[2–4]