Cricket song, wavelet graph. This image was produced by converting the sound frequencies of a singing male cricket (Gryllotalpa major) into a graph using a mathematical process known as wavelets. Wavelets reveal structure and detail that are not always visible in standard graphs of frequency over time (known as a spectrogram). This image has been plotted as a polar coordinate (circular) graph but wavelet graphs can also be in rectangular form. Male crickets produce a chirping 'song' by rubbing together comb-like appendages on their wings. Image created by Mark Fischer from Aguasonic Acoustics, USA.