Two dimensional acoustic images of sedimentary rocks were generated in order to characterize centimeter-scale heterogeneities and microstratigraphy. The images are based on dense sampling of the compressional phase velocity at frequencies near 1 MHz. The acoustic observations are compared to visual and x-ray images of the same samples. The results are intrepreted in terms of microscopic compositional velocities. Sedimentary rocks are more variable on the scale of a centimeter than we expected. The homogeneous Berea sandstone exhibits a ¿3% random variation in velocity. Heterogeneous rocks show 20 and 30% velocity variations. In the particular case where porosity is the sale compositional inhomogeneity, the acoustic and radiographic images agree. In general however, the acoustic images yield different information from the visual and radiographic images.