Abstract
We have measured the sound velocity and attenuation of the ortho-I single-phase YBa2Cu3Oy, which has a superconducting transition temperature of about 90 K, and compared them with the tetral-II single-phase YBa2Cu3Oy, which is a semiconductor. The sound velocity of the ortho-I has an additional increase below Tc, which is not observed in the tetra-II. This anomaly may be related directly to the superconductivity of this material. This is not explained by thermodynamic analysis.