Fig. 1.

Setup for the generation and detection of acoustic plane waves. Abrupt local heating of a silicon wafer by nanosecond laser pulses leads to the emission of strong broadband ultrasonic plane waves. Porcine subcutaneous fat tissue in the propagation path induces frequency dependent attenuation of the acoustic signals. The fat tissue is fastened between two aperture disks applying a small axial force on the tissue. Distance bolts with 6 mm or 20 mm ensure two precise lengths of the attenuation path. For these two lengths, attenuated acoustic plane waves were detected by an unfocused piezoelectric transducer, which was aligned by worm screws to ensure a one-dimensional signal propagation and detection. Image from https://doi.org/10.3390/jimaging5010013 by Burgholzer et al. was edited and is used under CC BY 4.0.