We report on a study of the far-infrared reflection for a sintered YBa2Cu30 7 sample that contained a large portion of preferentially oriented crystallites with the a-b plane parallel to the surface and that showed extraordinary high far-infrared reflectivity. From experimental reflection data we determined, by Kramers-Kronig analysis, the dynamical conductivity and extracted the contributions due to free charge carriers and phonons, respectively. We find evidence for an anomalous behavior of the dynamical conductivity at temperatures above T~; the dynamical conductivity increases strongly for temperatures approaching T~ and is strongly frequency dependent. By use of the Mattis-Bardeen theory we obtain an estimate for the superconducting energy gap of 2A/kT~_4.6 (for T< T~).We find that the lowest frequency infrared-active phonon mode is less damped in the superconducting state than in the normal state.