Videos are circulating online where users joke about the “heavenly sounds” of electric cars. However, scientists find these warning sounds to be flawed.
Researchers from Chalmers University of Technology in Sweden reveal that when electric cars share the same signal type, it becomes harder for pedestrians to locate the warning sound, especially when several electric cars are involved.
In their study, the researchers share the findings of their test, in which they asked people to locate three common types of warning signals (also known as AVAS, which stands for Acoustic Vehicle Alerting System) from hybrid and electric vehicles when they’re moving at low speed.
The research revealed that all signal types were harder to detect than the sound of an internal combustion engine.
When testing one of the signals, participants couldn’t say from which direction the sound was coming or whether it was one or a few cars at once.
The requirements for car manufacturers focus on the fact that it should include some kind of detection, but not on how pedestrians will be able to locate it or separate from other vehicles, explained Leon Müller, a doctoral student at the Department of Architecture and Civil Engineering at Chalmers via Science Daily.
According to international standards, electric and hybrid vehicles must include acoustic warning systems. These signals are sent when a car is going below 20 kph in Europe, China, and Japan, and 30 kph in the United States.
Wolfgang Kropp, a professor of acoustics, noted that the issue stems from the fact that when car manufacturers design their signature sound, it’s being tested in environments that are different from the noises that people face in reality.
The researchers tested 52 subjects, who were placed in a soundproofed anechoic chamber. There, 24 loudspeakers created sounds similar to those heard in a car park.
The scientists played three types of simulated vehicle sounds, resembling the signals from one or more electric or hybrid vehicles. The participants heard the signals from about 7.5 meters away, and they were also mixed with some background noise.
Once they heard the signal, participants had to determine from which direction the sound was coming as soon as possible. The test revealed that participants had a hard time locating a signal with two tones coming from three different vehicles simultaneously. None of the participants could manage to locate all the two-tone signals within 10 seconds.
The test also revealed that its participants had no problem locating sounds from an internal combustion engine.
This could be due to the fact that participants were familiar with this sound and found it easier to understand than the acoustic warning signals, Müller explained.
While the electric cars are known for being quieter than internal combustion engines, the fact that people can’t locate them for safety reasons could be a serious problem.
With this test, researchers are trying to learn more about how people react in situations involving electric and hybrid vehicles, with the goal of eventually increasing traffic safety.
Their follow-up study focuses on AVAS signals and how they affect non-road users.
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