“…As an example, results from a traditional wave spectroscopy analysis (Van den Abeele et al, 2000;CamposPozuelo et al, 2006;Goursolle et al, 2008) may be biased by the low amplitude of the higher order harmonics (or sub-harmonics) generated (Antonaci et al, 2010), which are frequently submerged within the noise level. As an alternative, we have recently proposed a scaling subtraction method (SSM) (Scalerandi et al, 2008a; et al, 2009) which allows to detect the influence of the nonlinearity of the sample on the portion of the signal at the fundamental frequency, with benefits in terms of signal-to-noise ratio. We have shown elsewhere the sensitivity of the method both to the presence of nonlinearity (Scalerandi et al, 2008b) and to its evolution (Bruno et al, 2009).…”