TOWARDS MODELING DYNAMIC HEAD-ABOVE-TORSO ORIENTATIONS IN HEAD-RELATED TRANSFER FUNCTIONS

Abstract

The torso and shoulder affect the head-related transfer function (HRTF) by means of reflection and diffraction. The reflection is strongest if the ear, source, and shoulder are approximately aligned and superimposes a comb-filter upon the HRTF magnitude spectrum that can have a depth of up to 5 dB above approximately 700 Hz. In case the direct sound path to the ear is obstructed by the shoulder or torso, they act as a low-pass with a high frequency damping starting at approximately 1 kHz and reaching up to 20 dB at 20 kHz. However, relatively little is known about the exact nature of the torso effect for different head-above-torso orientations with current data being based either on simplified geometric models, a neutral head-above-torso orientation, or head-above torso rotations in a single plane. To close this gap, we aim at developing a 3D head and torso model that can rotate its head with three degrees of freedom based on a functional model of the average healthy young cervical spine. In this work, we introduce the parameterization of the model. The model can be used to numerically simulate HRTFs for the anatomically possible range of head-above-torso orientations and is intended to analyze the torso effect in more detail and to acoustically model dynamic head-above-torso movements for virtual acoustic reality.