The silence of electric cars is an asset for the environment… but it also poses a real safety headache. At low speeds, these vehicles can surprise pedestrians, especially visually impaired people, which is why manufacturers must integrate audible warning systems. The regulations impose a result, but leave great creative freedom regarding the type of sound used.
How to report the presence of a silent vehicle?
At the head of a project carried out within the Acoustical Society of Japan, a team tackled this very concrete question: how to design a sound signal distinctive enough to warn, without becoming a nuisance? “ In our study, we sought to design approach sounds based on onomatopoeia evoking the image of a discrete vehicle », Explains researcher Mei Suzuki in a press release. The idea is not to simply add artificial noise, but to provide an intentional, understandable and immediately identifiable sound.
The approach is based on two main axes. On the one hand, sounds inspired by onomatopoeia (such as a discreet “hiss”) selected to correspond to the concept of a silent vehicle. On the other, the use of “pink noise”, a filtered signal which concentrates more energy in low frequencies. A complete library was created, then subjected to studio and real-world testing. Volunteers were asked to rate each sound based on several criteria, including how easy it was to notice and the sense of urgency it conveyed.
At the end of the tests, one candidate clearly stood out: low-frequency pink noise. This sound, less sensitive to interference from ambient noise, has proven to be the most effective in signaling the arrival of a vehicle, even in a noisy environment, whether heavy traffic or construction. “ The reason this sound stimulus was rated highest is its strong bass components and its similarity to the natural sound of a moving vehicle », specifies Mei Suzuki.
This result is just the beginning. The Japanese team now intends to adapt this work to micromobility, an area that is still little explored: electric bikes, scooters, small urban vehicles. “ We are conducting research this year on the design of approach sounds for these devices », Indicates the researcher. The objective is to reduce collisions involving pedestrians and vulnerable users, in cities where coexistence between modes of transport is becoming ever more complex every day.
Presented at a joint conference of American and Japanese acoustic societies in Honolulu, the study offers manufacturers a clear framework for designing the future sounds of electric vehicles. A guide that is all the more important as the streets and their users must learn to deal with a rolling stock that is ever quieter but not invisible.
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