'Pink noise' beats other tones as top alert for whisper-quiet EVs

Researchers led by graduate student Mei Suzuki at the Acoustical Society of Japan addressed the safety challenge posed by the near-silent operation of electric vehicles (EVs) at low speeds. Because EVs lack traditional combustion engines, they produce minimal noise, creating hazards for pedestrians who may not notice their approach. Automakers are required to install alert sounds, but the specific sounds vary widely. Suzuki’s team aimed to design purposeful, easily recognizable approach-warning sounds inspired by onomatopoeia and pink noise, focusing on signals that naturally convey the presence of a quiet vehicle. Through testing a library of sounds both in controlled studio environments and real road conditions, the researchers found that a particular low-frequency pink noise was rated highest for noticeability and urgency. This pink noise, characterized by greater energy in lower frequencies, was less likely to be masked by ambient sounds like traffic or construction, making it effective for alerting pedestrians. The sound’s similarity to traditional automotive running noise contributed to its effectiveness. Building on these