Abstract: A new cement formulation includes a base cement slurry and an admixture of acoustic metamaterial particles, the acoustic metamaterial particles each having a dense inner core and compliant surrounding matrix. The cement formulation exhibits a substantial increase in transmission loss over the base cement slurry at a first frequency, and does not exhibit a substantial increase in transmission loss over the base cement slurry at a second frequency. A new cement interrogation technique involves transmitting acoustic energy at and near the band-gap frequency of an acoustic metamaterial, detecting an acoustic response and analyzing it for band-gap performance involving substantially elevated transmission loss at or near a given first frequency that rapidly falls off at nearby frequencies, determining that the cement formulation is present in regions exhibiting band-gap performance, and determining that the cement formulation is not present and/or has been compromised in regions not exhibiting band-gap performance.