Auditory model-based estimation of the effect of head-worn devices on frontal horizontal localisation

Ville Pulkki,Petteri Hyvärinen,Pedro Lladó

doi:10.1051/aacus/2021056

Abstract

Auditory localisation accuracy may be degraded when a head-worn device (HWD), such as a helmet or hearing protector, is used. A computational method is proposed in this study for estimating how horizontal plane localisation is impaired by a HWD through distortions of interaural cues. Head-related impulse responses (HRIRs) of different HWDs were measured with a KEMAR and a binaural auditory model was used to compute interaural cues from HRIR-convolved noise bursts. A shallow neural network (NN) was trained with data from a subjective listening experiment, where horizontal plane localisation was assessed while wearing different HWDs. Interaural cues were used as features to estimate perceived direction and position uncertainty (standard deviation) of a sound source in the horizontal plane with the NN. The NN predicted the position uncertainty of localisation among subjects for a given HWD with an average estimation error of 1°. The obtained results suggest that it is possible to predict the degradation of localisation ability for specific HWDs in the frontal horizontal plane using the method.

Highlights

Head-worn devices (HWDs), such as helmets or hearing protectors, may obstruct the acoustic transmission of sound to the ear completely or partially
The aim of this study is to develop tools to evaluate HWDs as an alternative to running standardised listening tests, which narrows down the task quite prominently
The data of subject 6 was discarded from analysis due to an abnormal strategy on responding when front-back confusions were encountered, responding always 90° when the sound was perceived from the back. Apart from this aforementioned subject, two trials were discarded from analysis, since it appeared clear that a mistake had been made using the user interface which had a high impact on the neural network performance

Summary

Introduction

Head-worn devices (HWDs), such as helmets or hearing protectors, may obstruct the acoustic transmission of sound to the ear completely or partially. Models of spatial hearing aim at emulating the functions of the auditory system that are related to the localisation of sounds. The inputs to the model are usually the acoustic signals that reach the two ears, and the direction of arrival is estimated based on, e.g., spectral features of the individual signals (monaural cues), or the differences in timing, level, and similarity between the two ears (binaural cues). When the location of a sound source is restricted only to the frontal horizontal plane, binaural cues are typically enough to resolve the direction of the sound. An auditory model that does not take advantage of the monaural cues suffices when the localisation task is limited to the frontal horizontal plane, as in the current study. Binaural auditory models can be found in The Auditory Modeling Toolbox by Søndergaard and Majdak [3] (i.e. [4,5,6]), and are included in the book The technology of binaural listening, by Blauert et al [7]

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