The reason an electric car is given an invented hum

Electric vehicles are quiet enough to surprise a pedestrian at walking speed. Regulators responded by requiring a minimum external sound — an Acoustic Vehicle Alerting System — that the manufacturer must design. The hum is entirely artificial: the motor produces almost no noise, so the car plays a sound through external speakers. The challenge is making the hum audible without being annoying, futuristic without being alien, and identifiable as a car without mimicking the combustion engine it replaced.

What everyone sees

A pedestrian hears a gentle hum approaching and steps aside. The sound feels natural — like what an electric car should sound like. The pedestrian does not realise the sound was invented from scratch; she treats it as the car’s natural voice, not as a speaker playing a designed file.

What is actually happening

Research on pedestrian safety and quiet vehicles shows that silent cars are significantly harder to detect at low speeds, increasing accident risk for pedestrians and cyclists. Regulations such as UN Regulation No. 138 mandate minimum sound levels, and manufacturers invest in sound design that balances detectability with brand identity and aesthetic appeal.

Why it stays hidden

The hidden mechanism is a designed sensory signal replacing one that technology removed. The combustion engine warned pedestrians as a by-product; the electric motor does not. The artificial hum is a safety prosthesis — a sound the car does not need but the street does — and its design must solve a branding problem and a safety problem simultaneously.