This work discusses the possibilities of some novel applications for the high frequency (200 kHz–500 kHz), high sensitivity (-20 dB– -35 dB) and wide band (> 50 % @ -20 dB) air-coupled transducers that have been used so far for non-destructive testing and materials characterization at CSIC. These applications refer to non-contact human-machine interfaces, gesture recognition and echolocation. Compared with other technologies, the relatively higher frequency and bandwidth permit to achieve better resolution and the higher sensitivity permit to reach longer distances. In addition, this later feature also permits to reduce the number of transducers. This is achieved by using a conical reflector that provides an omnidirectional (2D) acoustic field. Examples of applications and realizations are shown by using single element 250 kHz transducers; and 8-elements 400 kHz sectorized array transducers. This later type of air-coupled array is introduced here for the first time.
This research was funded by grant (DPI2016-78876-R-AEI/FEDER, UE) from the Spanish State Research Agency (AEI) and the European Regional Development Fund (ERDF / FEDER).