A low whistle rolls on the street, a completely unfamiliar sound.
It looks like a flying saucer or like the spaceship Enterprise from "Star Trek".
E-cars sound different than conventional ones - and that is definitely wanted.
There is a rethinking of electric cars: “For years, manufacturers have tried to make their vehicles quieter.
Now they have to deliberately give them a sound, ”says Stefan Sentpali, Professor of Acoustics, Dynamics and Vehicle Technology at the University of Munich.
E-cars start so quietly that accidents can happen.
Therefore, the legislature requires an acoustic signal effect, the so-called Approaching Vehicle Alert System (AVAS), for newly type-approved hybrid and electric vehicles.
Within the EU, all vehicles up to 20 km / h and when reversing must produce a noise level of at least 56 dB and a maximum of 75 dB, the sound must be continuous.
This is the only way that other road users, including the visually impaired, can precisely locate the vehicles.
E-cars shouldn't creak or grunt
“How the cars sound exactly is up to the manufacturers.
It can be emotional or sober, the only important thing is that it sounds like a vehicle, ”explains Professor Sentpali.
Sounds have been helping people classify properties and provide orientation for thousands of years.
“People have a certain expectation of how an object sounds,” says Sentpali.
This also applies to an electric car: “The sound must be of high quality, it must not creak or grunt.
We associate this with harmful and interference noises. ”The only question is how exactly electric vehicles should sound, because there has not yet been any empirical data on this.
That would be too quiet in some driving situations, so the legislature requires an acoustic signal
“People know what vehicles sound like in science fiction films.
They will also use this as a basis for electric vehicles.
They sound up to two octaves higher, more high-frequency, like a quiet, pleasant whistle, ”says Professor Sentpali.
The design option lies not with the fundamental tone, but with the overtones.
Sound design for e-cars with the help of musicians
Indra Kögler is a sound designer at Volkswagen.
Together with Klaus Zyciora, Head of Design for the VW Group, and the musician Leslie Mandoki, VW has developed a futuristic sound for its ID electric series in recent years.
Good sound design only works if it helps and is not intrusive.
The art is to create a sound for different groups that everyone perceives as pleasant and not annoying: "E-mobility feels different and drives differently, so it can sound different," explains Zyciora.
“We wanted to create a sound profile for the ID family that sounds full of character, futuristic and different from conventional vehicles.
Passers-by should hear straight away that the future is driving by. "
E-cars can also be recognized by their sound
Future ID model series will, however, differ in terms of the sounds.
“Depending on the size of the model, the vehicles sound different.
A small car now also makes different noises than a large limousine, ”explains Indra Kögler.
The e-cars also sound new in the interior, for example with the warning sounds and feedback from the voice control.
“The interior has to fit into the new era, including the sound of the turn signal and the ready-to-drive sound, which hugs the occupants with its lively and soothing tones,” says Indra Kögler, describing the goal.
For Thomas Küppers, an e-vehicle has to sound different, especially inside: “E-machines work quietly, which benefits the interior.
The nicest sound in the car is the absolute silence, ”says the Mercedes sound designer.
Mercedes therefore attaches great importance to an almost silent drive.
Sound of Silence?
No, in many electric cars typical sounds for greeting, starting or other situations belong to the sound family, here the ID.3
In future electric models such as EQS and EQE, there should also be emotional driving sounds that change when you accelerate.
Five sound designers develop sound worlds for this - not in the studio, but in the respective vehicles.
“For many drivers, acoustic feedback from the engine creates additional confidence and a real driving experience,” says Küppers.
Different sound worlds or sound packages that can be adjusted like radio stations are conceivable.
These include unexcited, classic, puristic as well as futuristic and expressive tones.
It is important for all sounds that they are reproducible without disturbing resonances and that they sound high quality.
The sounds for e-cars are not canned
The sound family in an e-car includes the greeting, starting, readiness to drive, selecting gear, changing the driving program and the drivetrain noises.
The driving noises are not finished MP3 or Wave files, but individual sounds from a real-time calculation.
“The sound changes depending on the driving conditions.
There is a lot of computing power behind it, ”says Küppers.
For the outdoor area, Mercedes does not compose a prominent brand sound as AVAS.
"Our legally prescribed warning noises are limited to a synthetic, noise-like rolling noise", explains Küppers.
Depending on the country-specific legislation, they could slowly turn the sound down from around 20 to 30 km / h: "We don't want to produce any unnecessary noise because we are wasting the potential to make cities quieter."
Shaping the invisible: Renzo Vitale is responsible for the e-car sound at BMW
Renzo Vitale is responsible for the e-car sound at the BMW Group.
With the Mini Electric, this includes the prescribed driving noise and the sounds in the interior.
"I try to translate the aesthetic elements and moods that make a Mini into sound," says Vitale.
That sounds abstract, but works with the help of a translation of the light field into a sound field: "This is how light reflections on the water sound diffuse and soft."
The sound can change with tempo
The electric mini should surprise you when you start it.
A two second long sound can be heard subtly.
“When stationary, the electric car should sound friendly, light and bright, while driving it should sound sporty and dynamic,” says Vitale.
“The only thing we keep from conventional drives is the ratio of sound to revs and speed,” says Vitale.
The whims of the young mini: The soundscape of the Mini Electric can change from friendly, light and bright when stationary to sporty and dynamic when driving
In future BMW e-cars, acoustic feedback should become more important.
With Hollywood film composer Hans Zimmer, Vitale is developing various soundscapes for the interior for upcoming models, which are intended to provide an even more emotional driving experience: "This turns the driver into a composer and the car into an instrument, creating a really great sound experience."
Sound tinkerer: Film composer Hans Zimmer (l) and Renzo Vitale are working on the soundtrack of a BMW vehicle