ELECTRIC CARS CONFUSE OUR EARS – WE HEAR THEM, BUT CAN’T PLACE THEM

We can hear electric cars but have no idea where they are, according to new research.

A study from Chalmers University of Technology in Sweden shows that one of the most common signal types is very difficult for humans to locate, especially when multiple similar vehicles are in motion simultaneously like in a supermarket car park.

Researchers investigated how well people can locate three common types of warning (or AVAS -Acoustic Vehicle Alerting System) signals from hybrid and electric vehicles moving at low speeds.

The researcher’s tests showed that all the signal types were harder to locate than the sound of an internal combustion engine.

For one of the signals, the majority of test subjects were unable to distinguish the direction of the sound or determine whether they were hearing one, two or more vehicles simultaneously.

Leon Müller, a doctoral student at the Department of Architecture and Civil Engineering at Chalmers, said: “The requirements placed on car manufacturers relate to detection, or detectability, not about locating sound direction or the number of vehicles involved.

“But if you imagine, say, a supermarket carpark, it’s not inconceivable that several similar car models with the same AVAS signal will be moving at the same time and in different directions.”

Wolfgang Kropp, professor of acoustics at the Department of Architecture and Civil Engineering at Chalmers, said: “The way the requirements are worded allows car manufacturers to design their own signature sounds.

“These warning signals are often tested without the complication of background noise. But in a real traffic environment there are usually many different types of sound.”

The experiments involved 52 test subjects and took place in Chalmers’ acoustics laboratory, using soundproof anechoic chambers to simulate real-world conditions like those in large car parks.

Participants sat at the centre of a ring of 24 loudspeakers playing three types of simulated vehicle warning sounds—two-tone, multi-tone, and noise signals—representing one, two, or multiple electric and hybrid vehicles, alongside the sound of an internal combustion engine.

These signals were played at about 7.5 metres away, mixed with background noise from a quiet city car park. Participants were asked to quickly identify the direction of each sound.

The two-tone signal from three vehicles proved the most challenging; none of the subjects could accurately locate all such signals within ten seconds.

In contrast, the internal combustion engine sound was easily located, likely because it consists of short pulses across all frequencies, making it easier for the ear to perceive and more familiar to listeners.

Existing research has focused mainly on detectability and what is usually referred to as “detection distance”. No previous studies have investigated what happens when two or three cars emit the same type of signal. The researchers see a major need for further knowledge of how people react in traffic situations involving electric vehicles.

“Naturally, as acousticians, we welcome the fact that electric cars are significantly quieter than internal combustion engines but it’s important to find a balance,” said Müller.

In a follow-up study, the researchers have begun investigating how AVAS signals are perceived and what effect they may have on non-road users.

2025-06-19T10:48:16Z