“…Nonlinear ultrasound, commonly known in the ultrasonic scientific community as nonlinear elastic wave spectroscopy (NEWS) techniques, is a family of ultrasonic inspection methods that have shown higher sensitivity to the detection and localisation of damage (material flaws and micro-cracks) at early stages of formation than linear ultrasound (Boccardi et al, 2018;Zagrai et al, 2008). NEWS methods can rely on higher harmonic generation (Buck et al, 1978;Ciampa et al, 2017;Fierro and Meo, 2019;Polimeno et al, 2010;Scarselli et al, 2017;Solodov, 2014), time reversal (Ciampa and Meo, 2012;Lints et al, 2017;Liu et al, 2015), wave modulation (Chrysochoidis et al, 2011;Dionysopoulos et al, 2018;Fierro and Meo, 2018;Klepka et al, 2014;Pieczonka et al, 2015;Van Den Abeele et al, 2000b), phase modulation (Vila et al, 2004), local defect resonance (Post et al, 2017;Segers et al, 2018;Solodov et al, 2015), imaging of nonlinear scatters (Haupert et al, 2017;Solodov and Busse, 2012) and shift in resonance frequency characteristics (Chakrapani et al, 2015;Polimeno and Meo, 2009;Solodov, 2018;Van Den Abeele et al, 2000a).…”