Binaural Reproduction of Plane Waves With Reduced Modal Order

Modal descriptions of measured or simulated sound fields using spherical harmonics enjoy popularity and the binaural reproduction of the respective datasets using headphones is of great interest. A common method to extract directional information in the space domain from an underlying modal description is using plane wave decomposition techniques. Usually a set of head related transfer functions (HRTFs) is involved in a next step in order to establish the typical binaural cues that can be evaluated by the human auditory system. Due to their nature, HRTFs carry substantial information in higher modal orders in proportion to the temporal frequency. Owing to different reasons, measurement or simulation systems often deliver a comparatively low number of resolvable modes. This leads to plane wave descriptions of limited modal order that entail substantial adaptation problems to HRTFs. The consequences of the modal mismatch are discussed. The adaptation can be optimized by appropriate spatial (re)sampling of the HRTFs. Nevertheless, considerable technical differences remain between a native HRTF and its resulting order-reduced counterparts. Listening experiments were conducted in order to evaluate some of the perceptual differences. Thus theoretical and perceptual aspects of the binaural reproduction of plane waves with reduced modal order are discussed.