Why electric cars are almost silent, and why they're made to make noise
EVs have no combustion engine, so they're very quiet at low speeds. That's why many countries require a special warning sound called AVAS.
In this article
Ever been startled when an electric vehicle (EV) suddenly glided past you in a car park? You're not alone. Electric cars really are very quiet, especially when moving slowly.
Where does a normal car's noise come from?
Petrol and diesel cars make noise from their internal combustion engine: small explosions of fuel, moving valves and the exhaust. EVs are driven by electric motors that make almost no sound.
At high speeds the difference isn't very noticeable, because most of the noise comes from tyres and wind. The real problem happens at low speeds, for example in housing areas, pedestrian crossings and car parks.
A danger to pedestrians
Pedestrians, cyclists and especially people with visual impairments rely on sound to detect approaching vehicles. Quiet cars are hard to notice, which raises the risk of accidents.
Did you know? The soft "hum" you hear from a modern EV moving slowly isn't the motor. It's an artificial sound played through a speaker on the outside of the car.
What is AVAS?
AVAS (Acoustic Vehicle Alerting System) is a system that automatically plays a warning sound when an EV or hybrid moves at low speed.
- In the European Union, Regulation (EU) No 540/2014 made AVAS mandatory for new types of electric and hybrid vehicles from July 2019, and for all relevant new vehicles from July 2021. The sound is required up to about 20 km/h and when reversing.
- In the United States, safety standard FMVSS 141 sets a minimum sound for electric and hybrid vehicles at speeds below about 30 km/h.
Above those speeds, tyre and wind noise is considered enough to warn people.
Specially designed sounds
Each carmaker designs its own AVAS sound. Some sound futuristic, others a gentle hum. The sound usually changes pitch with speed, so people nearby can tell whether the car is speeding up or slowing down.
The takeaway
Silence is one of an EV's comforts, but on the road it can be a risk. That's why modern electric cars are deliberately "given a voice", so every road user stays safe.
