Designing Audible Safety for Electric Vehicles to Improve Pedestrian Awareness
Electric vehicles have long been praised for their smooth and quiet performance, offering a welcome shift away from the combustion roar of traditional engines.
Yet their near-silent operation presents a challenge in crowded environments where pedestrians, cyclists, and vulnerable road users rely on auditory cues for safety. Regulators have responded by requiring manufacturers to equip EVs with approach sounds at low speeds, though most rules focus on basic volume thresholds rather than specifying the character or tone of the audio itself.
This broad regulatory freedom has opened the door for researchers and engineers to explore how bespoke acoustic signatures can improve safety outcomes. With the right design, an EV’s approach sound can cut through ambient noise, convey urgency when needed, and offer intuitive cues that allow pedestrians to perceive direction and speed. Researchers have begun to investigate which sound profiles offer the most effective balance between audibility and comfort.
Exploring Onomatopoeia and Pink Noise in Sound Design
Graduate student Mei Suzuki and her research team have pursued a distinctive approach to this challenge by exploring sounds inspired by onomatopoeia typically associated with quiet or subtle motion. She presented the group’s findings at the Sixth Joint Meeting of the Acoustical Society of America and the Acoustical Society of Japan, held in Honolulu, Hawaii.
Suzuki explained the team’s method: “In our research, we aimed to design approach-informing sounds based on onomatopoeia that [are] evoked by the image of a ‘quiet vehicle.’ These stimuli included sounds created based on onomatopoeic sounds and pink noise.” By weaving these intuitive sonic cues into each experimental audio clip, the team aimed to produce warning signals that felt natural rather than intrusive.
Pink noise, in particular, stood out as an appealing candidate because of its distinct frequency profile. Unlike white noise, which distributes frequencies evenly, pink noise emphasises lower tones, creating a sound that feels softer yet more robust in noisy conditions.
Real-World Testing to Evaluate Effectiveness
To validate their work, the researchers conducted a series of assessments in both controlled studio environments and real-world settings. Volunteers listened to each sound in a variety of acoustic landscapes and rated them using criteria designed to reveal how effectively each option communicated urgency, detectability, and clarity.
Participants evaluated statements such as:
- “The sound has a sense of urgency.”
- “The sound is easy to notice.”
- “The sound helps me understand that a vehicle is approaching.”
The trial produced a clear frontrunner. A customised variant of pink noise proved the most consistently effective, earning high marks for its recognisability and its ability to break through background noise.
Suzuki noted the reasoning behind the result: “The reason this sound stimulus was rated highest was its strong low-frequency components and its similarity to automotive running noise.” The lower frequencies offered a natural presence that echoed familiar traffic sounds, helping pedestrians register the vehicle’s approach without feeling startled.
Why Low-Frequency Profiles Work Best
One of the crucial advantages of low-frequency audio is its resilience in complex soundscapes. High-frequency noises can be easily masked by wind, traffic, conversations, and urban activity, but lower tones travel farther and retain clarity even when competing sources are nearby.
The team observed that their best-performing sound was significantly less vulnerable to being drowned out. This is particularly relevant in urban centres where EVs often operate amid dense layers of ambient noise. A well-designed auditory signature not only supports pedestrian awareness but also bolsters safety for visually impaired individuals who rely heavily on sound.
Extending Research to Micromobility Devices
With the rapid rise of electric bicycles, e-scooters, and other lightweight mobility solutions, similar auditory safety concerns have emerged. Many of these devices travel quickly but produce minimal sound, creating new challenges in pedestrian areas. Suzuki’s team is now extending its research to identify the best sound profiles for these vehicles.
She emphasised the importance of this next step: “Starting this year, we are conducting research on the sound design of approach warning sounds specifically for micromobility devices. Since research on approach warning sounds for micromobility devices is largely unexplored, we believe this could contribute to reducing collisions involving pedestrians and visually impaired individuals.”
This shift aligns with a growing body of global research that highlights the increasing safety risks associated with silent micromobility. Cities worldwide are piloting new rules requiring e-scooters to emit low-level alerts, and manufacturers are beginning to explore integrated speaker systems that produce subtle but distinctive tones.
Broader Landscape of EV Acoustic Research
Beyond this project, acoustical engineering teams across Europe, Asia, and North America are also exploring how best to strike a balance between safety and comfort. Studies from the European Commission and the US National Highway Traffic Safety Administration indicate that pedestrians identify approaching EVs more reliably when the warning sound includes harmonic complexity rather than a single synthetic tone. Automotive brands have responded with unique audio signatures, some even developed by professional sound designers and composers.
Manufacturers implementing these systems often consider:
- Psychoacoustic responses to tone and rhythm
- Environmental noise levels in key markets
- Consumer acceptance and brand identity
- Legal compliance across multiple jurisdictions
As cities become denser and transport networks grow more interconnected, the relevance of these acoustic strategies will only increase.
Advancing Safer Streets Through Better Soundscapes
Suzuki’s work contributes to a broader movement to reimagine how electric mobility interacts with public spaces. While EVs are a critical solution in reducing emissions and improving air quality, their silence is both a technological triumph and a safety challenge. Thoughtfully designed audio cues offer a simple and effective way to bridge that gap.
With ongoing research, including expanded studies on micromobility devices, the future of electric transport may include a more harmonised sonic environment that feels intuitive, safe, and unobtrusive. By understanding how people perceive sound in busy environments, engineers can fine-tune alert systems that support awareness without contributing to noise pollution.
These innovations promise to shape safer streets and more inclusive mobility networks as electric transport continues its global rise.
