Some measurements of the propagation of ultrasonic pulses through packs of spherical and nonspherical particles of different diameters are reported. The packings include evacuated and compressed media. The values of sonic velocity measured together with the measured bulk elastic properties of one such packing yield a reasonable value for Poisson's ratio, tending to 0.5 for the assembly. Increasing contact pressure between particles, or the presence of interstitial air affect the properties considerably.