Measuring grain roughness for the purpose of high‐frequency acoustic modeling

Grain roughness and packing are important sediment properties for newer acoustic models. We present the scanning electron stereomicroscopic imagery of natural sand grains of varying shape and roughness for evaluation of potential grain interactions of individual grains. The grain shape and the presence of microasperities will determine the probability of the contact with surrounding grains being a point or a larger area. Moreover, the use of a micro‐roughness power spectrum in characterizing the sand grain roughness may be appropriate. Grain contact information is an essential starting point for developing and evaluating acoustic models that address acoustic losses at high frequencies. This information provides the basis to understand contact mechanics, such as grain slip and frame dilation, during insonification. Because media frame stiffness depends, at the grain scale, on the number and type of grain‐to‐grain contacts, we characterize sand sediments with imagery identifying such grain contact information. The natural shapes of grains, their variations, and their packing density present a broad distribution of grain contact types and areas. X‐ray microfocus computed tomography captures volumetric images of grain interactions, which enable the grain contacts to be classified and quantified. The method and results of this evaluation with computed tomography will be also presented.