Comparing subjective similarity ratings and quantitative errors for the evaluation of free-field binaural panning techniques

Abstract

A free-field sound source can be accurately rendered over headphones via direct convolution with head-related impulse responses (HRIRs). Using binaural panning techniques, a free-field source can be approximated, which can be thought of as HRIR reconstruction. However, a loss of fidelity occurs related to the panning algorithm’s spatial resolution. Previously, perceptual comparisons of noise bursts were made between panned sources and direct convolution with measured HRIRs. Reconstructions were generated using five different binaural panning methods, both with and without time-alignment of the HRIRs with separate application of the interaural time delay (ITD). To further explore the listening test results, the quantitative differences between the reconstructed and original HRIRs were investigated alongside the perceptual data. Several perceptually-motivated error metrics were evaluated, including errors in both ITD and interaural level difference. The fidelity of the reconstructed HRTF magnitude response was evaluated using metrics that leveraged auditory modeling steps. Both subjective and objective results support that HRIR time-alignment reduces the number of filters needed for high perceptual accuracy. A principal component-base rendering filter set produced the best subjective accuracy with only a small number of required filters (16-25). The ability to predict perceptually detectable degradation via quantitative errors will be discussed.