This paper examines the range dependence of the HRTF for a simple spherical model of the head in both the time-domain and the frequency domain. The variation of low-frequency ILD with range is shown to be significant for ranges smaller than five times the sphere radius. The impulse response explains the source of the ripples in the frequency response, and provides direct evidence that the Interaural Time Delay (ITD) is not a strong function of range. Time-delay measurements confirm the Woodworth/Schlosberg formula. Numerical analysis indicates that the HRTF is minimum phase. Thus, except for time delay, the impulse response can be reconstructed from a simple principle components analysis of the magnitude response.

This paper examines the range dependence of the HRTF for a simple spherical model of the head in both the time-domain and the frequency domain. The variation of low-frequency ILD with range is shown to be significant for ranges smaller than five times the sphere radius. The impulse response explains the source of the ripples in the frequency response, and provides direct evidence that the Interaural Time Delay (ITD) is not a strong function of range. Time-delay measurements confirm the Woodworth/Schlosberg formula. Numerical analysis indicates that the HRTF is minimum phase. Thus, except for time delay, the impulse response can be reconstructed from a simple principle components analysis of the magnitude response.

In this paper, which is of programmatic rather than quantitative nature, we aim to further delineate and sharpen the future potential of the LISA mission in the area of fundamental physics. Given the very broad range of topics that might be relevant to LISA, we present here a sample of what we view as particularly promising directions, based in part on the current research interests of the LISA scientific community in the area of fundamental physics. We organize these directions through a "science-first" approach that allows us to classify how LISA data can inform theoretical physics in a variety of areas. For each of these theoretical physics classes, we identify the sources that are currently expected to provide the principal contribution to our knowledge, and the areas that need further development. The classification presented here should not be thought of as cast in stone, but rather as a fluid framework that is amenable to change with the flow of new insights in theoretical physics.