This paper describes the first use of the Transmission Line Modelling (TLM) method for the time-domain numerical modelling of sound propagation in odontocete acoustic tissue. The validity of the technique is assessed by performing simulations on the highly specialised lipid materials distributed within the melon of the species Phocoena phocoena. The geometrical data for the simulations was obtained from Computer X-ray Tomography (CT) scans published by T W Cranford. A time-discrete waveform based on the output from the animal was synthesised for injection into the TLM simulation. The software described accepts a 24-bit bitmap for the geometrical data, and the injected samples in a spreadsheet file. Output is available as pressures in another spreadsheet and a series of bitmaps showing the propagating waves at different points in time. A number of bitmaps may be generated from the program and combined using a readily available commercial program into moving wave visualisations. The model clearly shows the acoustic energy contained by the waveguide effect of the graded-index composition of the melon. The investigation supports the assertion that the melon is a wave guiding structure rather than a conventional lens. The tissue structures prior to the melon therefore appear responsible for generating the oscillatory waveform.