On the variation and invertibility of room impulse response functions

Abstract

This paper presents results concerning variations in impulse response functions measured in different rooms. The variation of these functions for changing source and receiver positions and orientation was examined by assessing the change in energies of the direct and reflected signal components. The various source/receiver positions and orientation examined during these tests correspond to typical positions occupied by human speakers in rooms. It was found that the response functions changed drastically with the variation of these recording parameters. The feasibility of inverting (deconvolving) such functions by using digital signal processing techniques was also examined. It was found that when the exact response function was employed, then such an operation was feasible, leading to enhancement and reduction in the reverberant energy present in signals (e.g., speech) recorded under similar conditions. However, when a response recorded at a different position in the same enclosure was employed, then, in general, the inverse filtering operation increased the distortions present in the signals. This indicates that signal dereverberation by impulse response deconvolution has a limited scope in most practical situations.