Provided herein are inspection systems and methods for detecting MTR present within a subsurface volume of a specimen. The approaches use acoustic transducers and, optionally, near-surface sensors to introduce inspecting energy into the specimen. Signal data representative of the inspecting energy is analyzed to detect MTRs. In some approaches, a shift in a frequency distribution of the signal data is determined. In other approaches, a distribution of values for a given characteristic of the signal data, such as amplitude or frequency, is computed and a quantified description of the distribution is computed. Response scores and/or intensity maps can be generated for the specimen based on the analysis of the signal data. MTR scores indicative of MTR in the specimen can be correlated to the response score and/or intensity map. The specimen can then be dispositioned based on the response scores and/or intensity map and their correlation with the MTR scores.