Psychoacoustic assessment of synthetic sounds for electric vehicles in a virtual reality experiment

TL;DR

Electric vehicles’ quiet operation can reduce detectability for pedestrians, motivating exterior sound regulations. The authors conduct a VR-based listening test with 14 participants across 15 EV exterior sound stimuli (pure, intermittent, combined tones, and double beeps) plus baselines, evaluating responses with 11-point scales and psychoacoustic metrics via the SQAT toolbox. Psychoacoustic measures, especially the Di et al. PA metric, best predict perceived annoyance (\(\rho \approx 0.89\)), outperforming conventional metrics like $L_{p,A,max}$. The findings inform safer, more acceptable exterior EV sound design and support regulatory standards that balance detectability with urban noise comfort, guiding future work toward broader stimuli, diverse listeners, and real-world validation.

Abstract

The growing adoption of electric vehicles, known for their quieter operation compared to internal combustion engine vehicles, raises concerns about their detectability, particularly for vulnerable road users. To address this, regulations mandate the inclusion of exterior sound signals for electric vehicles, specifying minimum sound pressure levels at low speeds. These synthetic exterior sounds are often used in noisy urban environments, creating the challenge of enhancing detectability without introducing excessive noise annoyance. This study investigates the design of synthetic exterior sound signals that balance high noticeability with low annoyance. An audiovisual experiment with 14 participants was conducted using 15 virtual reality scenarios featuring a passing car. The scenarios included various sound signals, such as pure, intermittent, and complex tones at different frequencies. Two baseline cases, a diesel engine and only tyre noise, were also tested. Participants rated sounds for annoyance, noticeability, and informativeness using 11-point ICBEN scales. The findings highlight how psychoacoustic sound quality metrics predict annoyance ratings better than conventional sound metrics, providing insight into optimising sound design for electric vehicles. By improving pedestrian safety while minimising noise pollution, this research supports the development of effective and user-friendly exterior sound standards for electric vehicles.

Figures (6)

• Figure 1: Scheme of the considered sound source and observer geometry bazilinskyy2023exterior.
• Figure 2: Spectrogram for the sound stimuli Combined tone, continuous, 2000 Hz (case No. 12).
• Figure 3: (Top) Example view of participant in VR environment. (Bottom) VR experiment at Eindhoven University of Technology.
• Figure 4: Example of a VR experiment in PALILA at Delft University of Technology. In practice, participants stood up during the experiment.
• Figure 5: Annoyance ratings per sound stimulus.