Supplementary data for the paper 'Exterior sounds for electric and automated vehicles: Loud is effective'

Exterior vehicle sounds have been introduced in electric vehicles and as external human-machine interfaces for automated vehicles. While previous research has studied the effect of exterior vehicle sounds on detectability and acceptance, the present study takes on a different approach by examining the efficacy of such sounds in deterring people from crossing the road. An online study was conducted in which 226 participants were presented with different types of synthetic sounds, including sounds of a combustion engine, pure tones, combined tones, and beeps. Participants were presented with a scenario where a vehicle moved in a straight trajectory at a constant velocity of 30 km/h, without any accompanying visual information. Participants, acting as pedestrians, were asked to hold down a key when they felt safe to cross. After each trial, they assessed whether the vehicle sound was easy to notice, whether it gave enough information to realize that a vehicle was approaching, and whether the sound was annoying. The results showed that sounds of higher modeled perceived loudness, such as continuous tones with high frequency, were the most effective in deterring participants from crossing the road. The tested intermittent beeps resulted in lower crossing deterrence than continuous tones, presumably because no valuable information could be derived during the inter-pulse intervals. Tire noise proved to be effective in deterring participants from crossing while being the least annoying among the sounds tested. These results may prove insightful for the improvement of synthetic exterior vehicle sounds.

车辆外部音效（exterior vehicle sounds）已被应用于电动汽车，并作为自动驾驶车辆的外部人机交互界面（external human-machine interfaces）。尽管过往研究已探讨过车辆外部音效对行人可察觉性（detectability）与接受度（acceptance）的影响，但本研究采用了全新的研究视角，聚焦此类音效在阻止行人横穿道路方面的效能（efficacy）。本研究开展了一项线上实验，共招募226名实验被试，向其播放多种类型的合成音效（synthetic sounds），包括内燃机引擎声（combustion engine sounds）、纯音（pure tones）、复合音（combined tones）与蜂鸣声（beeps）。实验设置了如下场景：车辆以30 km/h的恒定速度沿直线轨迹（straight trajectory）行驶，且无任何伴随的视觉信息。被试以行人身份参与实验，当他们认为可以安全横穿道路时，需按住对应按键。每一轮试次（trial）结束后，被试需对三项内容进行评估：该车辆音效是否易于察觉、是否提供了足够的信息以让其意识到有车辆正在接近，以及该音效是否令人厌烦。实验结果表明，建模感知响度（modeled perceived loudness）更高的音效（如高频持续音），在阻止被试横穿道路方面效果最佳。本次测试的间歇性蜂鸣声（intermittent beeps）相较于持续音，对行人横穿的阻止效果更差，推测原因是在脉冲间隔（inter-pulse intervals）期间无法从音效中获取有效信息。轮胎噪音（tire noise）在阻止被试横穿道路方面表现出良好效果，且在本次测试的所有音效中，其令人厌烦程度最低。本研究结果可为车辆外部合成音效的优化改进提供富有启发性的参考。