Exploring the Impacts of Background Noise on Auditory Stimuli of Audio-Visual eHMIs for Hearing, Deaf, and Hard-of-Hearing People

TL;DR

This study investigates how background noise impacts auditory signals in audio-visual eHMIs for pedestrians, especially DHH individuals, revealing that loud noise worsens experiences but supplementary auditory cues can help.

Contribution

It is the first to examine the effects of background noise on auditory eHMI stimuli for both hearing and DHH pedestrians using virtual reality experiments.

Findings

Loud background noise impairs pedestrian crossing experiences.

DHH pedestrians' crossing experiences differ significantly from hearing pedestrians.

Additional auditory cues improve crossing experiences under noisy conditions.

Abstract

External Human-Machine Interfaces (eHMIs) have been proposed to enhance communication between automated vehicles (AVs) and pedestrians, with growing interest in multi-modal designs such as audio-visual eHMIs. Just as poor lighting can impair visual cues, a loud background noise may mask the auditory stimuli. However, its effects within these systems have not been examined, and little is known about how pedestrians -- particularly Deaf and Hard-of-Hearing (DHH) people -- perceive different types of auditory stimuli. We conducted a virtual reality study (Hearing N=25, DHH N=11) to examine the effects of background noise (quiet and loud) on auditory stimuli (baseline, bell, speech) within an audio-visual eHMI. Results revealed that: (1) Crossing experiences of DHH pedestrians significantly differ from Hearing pedestrians. (2) Loud background noise adversely affects pedestrians' crossing experiences. (3) Providing an additional auditory eHMI (bell/speech) improves crossing experiences. We outlined four practical implications for future eHMI design and research.