Researchers Develop More Audible Approaching Sound for Electric Cars
Approaching sounds from electric cars are primarily intended to protect vulnerable road users. Researchers are looking for the best sound for this purpose.
Test subjects listen to the approaching sound of an electric car at different distances and evaluate it.
(Image: Mei Suzuki)
A team of scientists from the Acoustical Society of Japan has developed a special approaching sound to help road users better perceive approaching, quiet electric cars. The sound is based on onomatopoeia and pink noise and is intended to be more perceptible than previous approaching sounds for electric cars. This is expected to minimize the risk for pedestrians and cyclists, for example.
In Germany, as in many other countries, an artificially generated warning signal, the Acoustic Vehicle Alerting System (AVAS), is mandatory to alert other road users to an approaching electric car traveling at speeds below 20 km/h. In this speed range, electric cars are usually so quiet that they can be easily overlooked. The approaching sound is not fixed. In principle, any car manufacturer can create their own warning sound. However, these are not always easily audible in all traffic situations.
The researchers at the Acoustical Society of Japan wanted to develop an approaching sound that is difficult to overlook, as the scientists presented at the Sixth Joint Meeting of the Acoustical Society of America and Acoustical Society of Japan, which takes place in Honolulu, Hawaii, from December 1st to December 5th. The scientists investigated what options exist to create stimuli that naturally convey the presence and approach of an electric vehicle.
Onomatopoeia and Pink Noise
They designed sounds based on onomatopoeia, the linguistic imitation of sound events associated with a specific event, such as a hiss, to evoke the association of a "quiet" electric vehicle. The researchers combined these sounds with 1/f noise, also known as pink noise. In pink noise, the amplitude decreases as the frequency increases. Low frequencies dominate. An average person perceives all audible frequency ranges as almost equally loud.
Based on this, the team of scientists created a sound library that they tested on test subjects in two environments: in the laboratory and under real road conditions. This ensured that the results were practical. The test subjects were tasked with evaluating the sounds, for example, whether they conveyed a certain urgency and whether they were easily perceptible. The sounds were then ranked according to these criteria.
Videos by heise
A sound with a high proportion of pink noise was judged to be the best. This is because the sound has strong low frequencies, similar to those of an internal combustion engine. The distribution of low-frequency sounds was less masked by ambient noise, so approaching electric vehicles equipped with it are "clearly audible under all conditions," the researchers write in a statement.
The scientists have since expanded their research and are now investigating which sounds are suitable for smaller vehicles such as e-bikes and e-scooters. Here too, the researchers aim to increase road safety and help prevent collisions with pedestrians and other road users.
(olb)
