Auditory warnings for electric vehicles: Detectability in normal-vision and visually-impaired listeners

Abstract

Electrical vehicles operating at low speed are often too quiet to be detected by pedestrians in time. In order to study the efficiency of additional auditory warning signals they might be equipped with, a sample of 100 sighted and 53 blind listeners was exposed to a virtual roadcrossing scenario in which they had to detect whether an approaching vehicle came from the right or left. Nine warning signals, designed to differ in particular sound features such as FM, AM or the number of harmonics were studied and compared with the recording of an unfitted electrical vehicle (EV) and a conventional diesel car. The responses measured in the scenario in which cars approached at irregular intervals over two 20-min periods showed no reaction-time differences between blind and sighted participants, and a significant advantage when listening under dry weather conditions as opposed to recordings mixed with the sound of rain. Most importantly, however, regardless of listening conditions and the population studied (sighted or blind), the additional warning signals differed greatly in efficiency. Some signals facilitated detection of the EV as much as making it as noticeable as a control diesel car of significantly higher sound pressure level. Other signals were largely ineffective compared with the unfitted EV. Analysis of the signal characteristics suggested a relatively low number of harmonics, absence of frequency modulation, and irregular amplitude modulation to be the most salient features facilitating timely detection.

Timbre, Sound Quality, and Sound Design

“…Such sounds must be heard in the acoustic situation of normal traffic. Accordingly, studying the quality of such sounds must consider the detectability of sounds in such an environment (Parizet et al 2014). More generally, Sect.…”

HindSight

“…Sonification can increase detectability of approaching vehicles in environments with background noise [17,22], especially in the case of quiet electric vehicles [24,23]. Diedrichs and Parizet separately describe design principles for sonifying approaching vehicles, such as amplitude modulation, pitch, and rhythm [8,31]. Hind-Sight leverages these design principles to generate audio to alert the user of oncoming vehicles outside their visual field.…”

Optimization of the Sound of Electric Vehicles According to Unpleasantness and Detectability

“…Electric vehicles (EVs) and hybrid vehicles are becoming a serious alternative to internal combustion engine cars (Gillibrand et al, 2011). However, at low speed (under 40km/h), EVs are very quiet and may be dangerous for pedestrian or visually impaired peoples who have to rely on auditory cues when intending to cross a road (Parizet et al, 2014). Regulation concerning the sounds of electric cars is still under study.…”

“…There is then clearly a conflict between detectability and annoyance for the perception of EV sounds. Different studies addressed this problem (Campillo-Davo and Rassili, 2016), (Lee et al, 2017), (Parizet et al, 2014). All these studies are based on hearing tests of a predefined set of sound stimuli.…”