Electric cars: Sound designers create sounds for the vehicles

Electric cars are very quiet at low speeds. As this poses a risk to pedestrians, new vehicles must produce artificial noise. This requires creative sound designers

Persistent traffic noise is annoying and can lead to mental problems – this has been proven in numerous studies. That’s why scientists have been researching for decades how to make vehicles, especially road and tire noise, as well as roads, quieter. With the first electric cars, however, a debate arose in the 2000s that went in the opposite direction: It was now said that the quiet electric motor could pose a safety risk in road traffic.

The vehicles with internal combustion engines that still dominate today can be heard even when stationary with the engine running. Many associations of the blind and partially sighted, however, fear that electric cars could hardly be heard acoustically when driving slowly. It is not about rejecting e-mobility, as the “European Blind Union” (EBU) emphasizes in a 2019 publication: “The EBU clearly supports the reduction of CO2 emissions through the use of electric cars. The EBU has spent the last decade on to fight for a solution to the threat posed by low-noise vehicles. “

The EBU and other advocates for increased road safety have already made some progress. For example, EU Regulation No. 540/2014, adopted in 2014, states that new electric cars must be equipped with an Acoustic Vehicle Alerting System (AVAS): Since July 2019, this Regulation has been applicable to new models with hybrid or electric drive , since 2021 for all newly produced vehicles of this type. Older Stromer can, but must not be retrofitted.

Artificial sounds for cars are controversial

The rule is not without controversy. “We believe that the European Commission’s regulation is completely wrong,” said the renowned car expert Ferdinand Dudenhöffer, director of the Center “Automotive Research” Institute (CAR) in Duisburg. In his view, progress in reducing traffic noise should not be offset by artificial noise. Instead, he and his colleagues rely on assistance systems, both for the blind and other disabled and for new vehicles, such as automatic emergency braking systems.

Dudenhöffer refers to a study from his institute from 2011. At that time, CAR conducted three test series with acoustic and perception tests with a total of 240 test persons. Of the participants, 14 percent were hearing impaired and 20 percent were blind or partially sighted. The investigations were carried out with eleven vehicle types with different drives (electric, petrol, diesel engines). As a result, researchers found only small differences in perception between electric vehicles and internal combustion engines at speeds of 30 and 40 kilometers per hour. The authors of the study wrote that there were only clear differences when driving at high speeds or at full throttle.

Fuel can be saved with start-stop systems that turn off the engine even when the vehicle is parked for a short time; therefore, more and more gasoline engines are being equipped with it. “When these cars are at the traffic lights, they can be heard just as little as electric cars,” Dudenhöffer emphasizes. Either the AVAS warning system should be used in all stationary vehicles, regardless of driving, or in no vehicles – the car expert is in favor of the second option. He also criticizes many studies because the acoustic perception of most people is not objective: Red and black cars are perceived as taller than vehicles with lighter colors.

The Federal Environmental Agency (UBA) is also more on the side of those who want to reduce noise. E-cars are quieter than others at low speeds. According to UBA, however, the rolling noise from the tires on the road surface dominates from around 30 kilometers per hour, “so the benefits in terms of noise emissions from electrically powered vehicles compared to vehicles with internal combustion engines do not apply.” writes the final report “Noise assessment of the Acoustic Vehicle Alerting System (AVAS)” from September 2021.

UBA recognizes that the AVAS warning system is necessary in the transition phase to predominantly electric traffic. At the same time, however, experts warn: “A regular review of the specifications of AVAS systems can lead to an improvement in warning quality while minimizing acoustic emissions.” UBA is also dependent on other road safety measures, such as improved accident analysis, additional units for the disabled and driver assistance systems.

On the other hand, Ercan Altinsoy from the Technical University of Dresden found clear differences between electric cars and petrol engines. From 2009 to 2013, he studied in a team with other researchers at TU Dresden the acoustic perception of low-speed vehicles. Among other things, it was about approaching cars with moderate acceleration in front of a moderately high background: “If an approachable vehicle with an internal combustion engine is perceived at an average distance of 36 meters, an electric vehicle traveling at the same speed is perceived only at an average distance. at 13 meters “, the researchers wrote.

The result was the same for cars approaching a parking lot: Vehicles with internal combustion engines were recognized on average one second after starting, electric cars only after three seconds. “In the assessment situation, this corresponds to a period in which a collision can already occur,” reads the study, which is published by the Research Association for Automotive Technology (FAT).

However, an AVAS sound, as required by the EU regulation, was not Altinsoy’s first choice. “One could, for example, measure the actual background noise and adjust the volume of the artificial sound accordingly,” he explains. However, this was too expensive and uncertain for the automotive industry. Other scientific proposals, such as the use of certain frequencies that are easily audible even at low volume, or visual pedestrian detection systems with targeted warning sounds, were also rejected.

Instead, EU Regulation No. 540/2014 of Annex VIII in 2014 provided: “The AVAS shall generate a continuous acoustic signal warning pedestrians and other road users of a vehicle in operation.” The sound system must also clearly indicate the behavior of the vehicle (acceleration, braking) up to a speed of 20 kilometers per hour and be comparable to the sound of a vehicle of the same class equipped with an internal combustion engine. Altinsoy reports that he initially advocated that all vehicles in the same class should make the same noise. But carmakers wanted to use the freedom in sound design that the regulation allows for brand-specific sounds.

Sound design for electric cars

Altinsoy eventually benefited from this because he received orders from several manufacturers to develop appropriate sounds. But how do you develop a vehicle sound? “It is similar to the visual design: one usually defines three criteria, for example, friendly, high quality, driving pleasure, and then tries to implement this in the sound.” Of course, the legal requirements had to be taken into account, and for established brands also past sound worlds. Familiar effects from music could be useful here: Harmonious sounds usually seem warm and friendly, while dissonant sounds can be taken as a warning.

In recent years, all car manufacturers have spent more or less effort on developing unmistakable sounds for AVAS. BMW even got Hollywood composer Hans Zimmer (“The Lion King”) into the recording studio. Musician and producer Leslie Mandoki became active for Volkswagen. But there is still enough work for the group’s own designers and acousticians.

“First and foremost, the sound must be understandable and authentic to passers-by,” explains Ingo Hapke, head of the acoustics team at Volkswagen. In addition, vehicle noise, such as rolling noises, can be detected. “But then an artistic component is added that embodies the character of the brand.” For Hapke, it is important that the sound does not interfere and that there are no unpleasant interactions with ambient noise or sounds from other vehicles.

VW took these and other arguments into account when developing the new ID series. “We created a whole new sound for our ID models. It was important for us to create a sound that passers-by connect directly to a vehicle – but at the same time represent something completely new,” says Indra-Lena Kögler, user -Experience Designer at Volkswagen and responsible for the overall sound experience in the ID models (User Experience: user experience). “The special thing about the sound of the ID family is that it is tuned to the visual design of the vehicles,” Kögler emphasizes. For example, the dynamic surfaces of the external sound are amplified by vivid depths.

Inside the vehicle, on the other hand, the sound effects are minimized and adapted to the light design. The smooth running of the electric motor should be noticeable to the passengers. “For us, the main feeling in the interior of the electric vehicles was the quietness; we adapted all the other interior sounds to this – meaning: you do not have to turn up the music system as much as with an internal combustion engine,” agrees Kögler. Although the acousticians and designers are happy with their work, Hapke is convinced that there is still enough work for him and his team: “We will get more feedback from customers who see the competition and stay up to date.” And maybe there will be a further increase in electric cars on the roads, then the politicians will change the AVAS rules again.

Stefan Parsch, dpa

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