Piezo emitters are also under development at ASH that operate at the frequency that has the maximum penetration range in concrete and can be developed for other structural materials. This allows ASH to utilize a sonar approach to detecting and mapping structural faults in foundations and other structural components. A single sensor of this type has demonstrated a sonar bi-directional acoustic penetration range in concrete of 5.5 meters. However, ASH is looking at a strategy of locating emitters and receivers at different locations to increase the spatial resolution as well as increase the operational range of this type of sensor.