This paper describes unusual applications of ultrasound that are based upon recent advances in transduction efficiency in air and gaseous media.

Piezoelectric transducer devices – capable of generating extremely high intensity ultrasound in ambient air up to 5 MHz – have been successfully developed and tested.  Besides their obvious uses for gas analysis, remote sensing, liquid level, gap, and thickness measurement, and proximity analysis, these new generation transducers now make it possible to analyze solids and liquids not only non-destructively, but also without physically touching transducers to the test medium.

Among various applications concerning the Non-Destructive Characterization (NDC) of industrial materials, we also describe the feasibility of a forensic application.  This concerns the detection of objects such as knives, guns, contraband drugs, dead bodies, etc., hidden inside false compartments or walls.

Evolution of Non-Contact Ultrasonic Analysis and its Applications for Hidden Objects Detections