The influence of spectral characteristics of early reflections on speech intelligibility

Abstract

The auditory system takes advantage of early reflections (ERs) in a room by integrating them with the direct sound (DS) and thereby increasing the effective speech level. In the present paper the benefit from realistic ERs on speech intelligibility in diffuse speech-shaped noise was investigated for normal-hearing and hearing-impaired listeners. Monaural and binaural speech intelligibility tests were performed in a virtual auditory environment where the spectral characteristics of ERs from a simulated room could be preserved. The useful ER energy was derived from the speech intelligibility results and the efficiency of the ERs was determined as the ratio of the useful ER energy to the total ER energy. Even though ER energy contributed to speech intelligibility, DS energy was always more efficient, leading to better speech intelligibility for both groups of listeners. The efficiency loss for the ERs was mainly ascribed to their altered spectrum compared to the DS and to the filtering by the torso, head, and pinna. No binaural processing other than a binaural summation effect could be observed.

Improving the conditioning of the optimization criterion in acoustic multi-channel equalization using shorter reshaping filters

“…Using a shorter reshaping filter introduces a trade-off between the condition number χ WĤ and the (weighted) least-squares error W(Ĥw − c d ) 2 2 . An appropriate filter length should incorporate knowledge about χ WĤ and W(Ĥw − c d ) 2 2 , such that preferably both quantities are kept as small as possible.…”

“…An appropriate filter length should incorporate knowledge about χ WĤ and W(Ĥw − c d ) 2 2 , such that preferably both quantities are kept as small as possible. Due to the arising trade-off between these quantities, the parametric plot of the condition number versus the (weighted) least-squares error for several reshaping filter lengths has an L-shape.…”

“…The corner of the L-curve, i.e., the point of maximum curvature, is located where the filter changes from being dominated by a large condition number to being dominated by a large (weighted) least-squares error. Hence, we propose to automatically select the reshaping filter length L auto g as the filter length corresponding to the corner of the parametric plot of the condition number χ WĤ versus the (weighted) least-squares error W(Ĥw − c d ) 2 2 . Figure 4 depicts a typical L-curve obtained using PMINT for acoustic system S 1 described in Section 6.1.…”

“…While early reverberation may be desirable [1][2][3], late reverberation may degrade the perceived speech quality and intelligibility [4][5][6] as well as the performance of automatic speech recognition systems [7,8]. In order to mitigate these detrimental effects of reverberation, several single-channel and A well-known complete multi-channel equalization technique aiming at acoustic system inversion is the multiple-input/output inverse theorem (MINT)-based technique [19], which however suffers from drawbacks in practice.…”

“…In order to increase the robustness against RIR perturbations, partial multi-channel equalization techniques, such as relaxed multi-channel least-squares (RMCLS) [23] and partial multi-channel equalization based on MINT (PMINT) [24], have been proposed. Since early reflections tend to improve speech intelligibility [1][2][3] and late reflections are the major cause of speech intelligibility degradation [4][5][6], the objective of partial equalization techniques is to shorten the overall impulse response by suppressing only the late reflections. While RMCLS imposes no constraints on the remaining early reflections, PMINT has been shown to be more perceptually advantageous since it also aims to control the remaining early reflections.…”