This paper considers the general problem of modeling pinna-related transfer functions (PRTFs) for 3-D sound rendering. Following a structural approach, we present an algorithm for the decomposition of PRTFs into ear resonances and frequency notches due to reflections over pinna cavities and exploit it in order to deliver a method to extract the frequencies of the most important spectral notches. Ray-tracing analysis reveals a convincing correspondence between extracted frequencies and pinna cavities of a bunch of subjects. We then propose a model for PRTF synthesis which allows to control separately the evolution of resonances and spectral notches through the design of two distinct filter blocks. The resulting model is suitable for future integration into a structural head-related transfer function model, and for parametrization over anthropometrical measurements of a wide range of subjects
