During the Sediment Acoustics Experiment in 1999 (SAX99), measurements were made of the sound speed and attenuation in a sandy sediment, supplemented by detailed environmental characterization. While the dispersion was consistent with Biot theory, the attenuation at high frequencies had a linear frequency dependence that was consistent with models based on losses at grain contacts. These results led to the development of a number of competing models of sound propagation in sand sediments. Subsequent to SAX99, measurements of sound speed and attenuation have been made in several ocean sediments as well as in a number of laboratory sediments composed of either sand or glass beads. Many of these experiments have been accompanied by careful measurements of the sediment properties and, in some cases, these properties have been varied to assess their impact on sound propagation. An overview of these results will be given and the implications of these measurements for high frequency sediment acoustics modeling will be discussed. [Work supported by the Office of Naval Research.]