Acoustic waveforms were formulated into seven feature configurations labelled 'A' to 'G'. The feature configurations are described visually in Fig. and verbally in Table , which also lists the number of features in each configuration. Config 'A' is the simplest, capturing the x-y position of the 'back wall echo' peak, and will be used as a benchmark. Configs 'B' and 'C' contain information from additional peaks. Config 'D' uses the entire time domain of each waveform excluding the first 1.9 µs segment, approximately, which is invariant in the dataset. Config 'E' is obtained by performing an FFT on config 'D', and keeping the magnitude spectrum of the first 300 frequency bins (0.12-37.0 MHz). This frequency range is slightly different compared to the previous chapter, because of the cropping of the first 1.9 µs that was applied to the time-domain. Config 'F' attempts to combine time-and frequency-domain information by concatenating configs 'D' and 'E' into one vector (not visualised in Fig. because the two domains have very different scales). Config 'G' has the same aim, but instead converts waveforms into spectrograms which reveal frequency changes over time and can be visualised as 2D images.