Boundary element simulations of the transfer function of human heads and baffled pinnae using accurate geometric models

This paper investigates various aspects of numerically modelled individualised head-related (and pinna-related) transfer functions (HRTF). The computer simulations are based on the exact solution of the wave equation using the boundary element method (BEM). The basic features of the HRTF are investigated with accurate geometric models of two heads and six pinnae which are captured by using state-of-the-art three-dimensional (3-D) laser scanners and digitisers. These computer models are converted to valid BEM models and their frequency response is simulated. We present the results of simulated HRTFs, and show the inter-variability of the response among six baffled pinnae modelled in identical conditions. With current computing hardware power, and vigilant optimisation of the manipulated mesh models and the solving procedures, heads with pinnae (but without torso) can be investigated at least up to 10 kHz, and baffled pinnae can be investigated up to 20 kHz. We conclude that it is possible to implement individualised HRTFs in a 3-D sound system or an auditory display, without the need for measurements in an anechoic chamber, if highly accurate 3-D images of the head and pinnae are captured and modelled with BEM.