[Sound Economy] Electric Vehicle Industry's Competition to Create Beautiful Noise

① The World of Electric Vehicle Virtual Sound Design
Genesis Uses Granular Method Combining Sound Decomposition
Hyundai Motor Enhances Ioniq 5 N Electric Vehicle Sound
BMW Collaborates with World-Renowned Hollywood Composer
Audi Finds Electric Vehicle Sound Materials from Everyday Noise

There was a time when the intense engine sound and exhaust note were symbols of supercars. The growling engine noise and the popcorn-like popping exhaust were hallmarks of high-performance vehicles. As we entered the era of electric vehicles, the noisy engine sounds disappeared. Compared to engines, electric motors produce almost no noise. As the interior became quieter, external noises started to become more noticeable. Automakers are now contemplating what kind of sound should fill the void left by the absence of engine noise.

Recently, global automakers have been putting great effort into electric vehicle sound design. Their goal is to create signature sounds that anyone can recognize and associate with the brand after just one listen. To achieve this, they collaborate with world-renowned composers or draw inspiration from natural and everyday sounds to create car sounds that mimic them. The key point of electric vehicle sound technology is how well they create unique sounds that fit the brand image and the vehicle. Additionally, it is important to seamlessly connect the sound with driving modes, speed, and accelerator pedal movements without any sense of incongruity.

Electric Vehicles Without Exhaust Sound Enhance Driving Enjoyment with Virtual Sounds

In 2021, Genesis applied the 'Electric Active Sound Design (e-ASD)' technology to its brand's first electric vehicle, the GV60. To introduce various sounds, they used a 'granular synthesis method' that breaks down sounds into very small units and recombines them to create new sounds. GV60 drivers can choose from three sound options: 'E-Engine,' which faithfully reproduces the sound of an internal combustion engine; 'E-Motor,' a newly crafted sound refined from the electric motor noise; and 'Futuristic,' which gives the feeling of riding a massive spaceship.

Furthermore, Hyundai maximized sound effects in the high-performance electric vehicle Ioniq 5 N, released in July this year. When selecting the 'Ignition' sound, which is inspired by internal combustion engine noise, drivers can hear the popcorn-like popping sound (pop and bang) from the exhaust. The 'Evolution' sound, which replicates the high-performance electric motor sound, is derived from Hyundai's high-performance hydrogen electric concept car N Vision Gran Turismo motor sound. Additionally, the 'Supersonic' sound, inspired by supersonic fighter jets, completes the set of three sound options.

The Ioniq 5 N allows you to choose one of three active sounds: Ignition, Evolution, or Supersonic.
Photo by Woo Su-yeon

BMW has been a brand serious about sound since the internal combustion engine era. In 2021, BMW entrusted composer Hans Zimmer with creating the electric vehicle sound. A former synthesizer musician, he is a maestro who has dominated Hollywood film music with works such as Gladiator, Interstellar, and Inception. BMW’s approach of viewing car sounds as a form of music aligns with the brand philosophy that values the 'emotion of driving.' BMW completed the 'Iconic Sound Electric' last year and first installed it in the brand’s first electric sedan, the i4. Since then, the 'Iconic Sound Electric' has been sequentially applied to BMW’s electrified lineup, including the XM, i5, and i7.

Composer Hans Zimmer (left in the photo) and BMW sound designer Renzo Vitale collaborating on the composition of the iconic sound "Electric"
[Photo by BMW]

Audi found the materials for its electric vehicle sounds in everyday life. The sound installed in Audi’s mid-large electric sedan e-tron GT originated from the end of a plastic pipe. Audi’s sound designers deliberately avoided spaceship sounds that might be heard in movies. Instead, they tried to draw inspiration from all kinds of instruments, from violins and electric guitars to the Australian Aboriginal traditional instrument, the didgeridoo. However, they could not find a satisfactory sound.

After various attempts, they attached a fan to the end of a narrow 3-meter-long plastic pipe and listened to the sound. This sound, reminiscent of a giant airplane flying at low altitude, became the basic material for the e-tron GT sound. They also created 32 sound samples, including synthesizer sounds, electric drill noises, and model helicopter sounds. They invited about 100 customers to conduct a blind sound test. By actively reflecting this consumer feedback, they were able to complete a familiar yet sporty electric vehicle sound.

Audi sound engineers Stephan Gissel and Rudolf Halbmeier are collecting the basic sounds of the E-tron GT by placing a fan against a plastic tube.
[Photo by Audi]

Quiet Electric Vehicles Without Noise... Considering Pedestrian Safety

Electric vehicles without engine noise must also consider pedestrian safety issues. According to data from the Korea Transportation Safety Authority, pedestrians can detect the approach of diesel vehicles from a distance of 10 meters, whereas the detection distance for electric vehicles is only 2 meters. This means that quiet electric vehicles could pose a safety threat to pedestrians, including those with visual impairments.

In Europe, since 2019, all new vehicles are required to be equipped with Acoustic Vehicle Alert Sound (AVAS) devices that emit vehicle noise externally. The United States also established AVAS mandatory installation standards in 2020, and South Korea enacted regulations mandating low-noise vehicle exhaust sound devices starting in July of the same year. Vehicles sold domestically must emit artificial noise (warning sounds) below 75 dB when driving at speeds under 20 km/h. Seventy-five decibels is roughly the noise level of a subway. Additionally, the frequency must vary so that pedestrians can perceive changes in speed. Just like musical scales, frequencies have highs and lows. The higher the frequency, the sharper and higher-pitched the sound becomes.

Hyundai Mobis has developed the world's first virtual engine sound system (AVAS).
[Photo by Hyundai Mobis]

To comply with these regulations, automakers typically install external speakers in the engine compartment, bumper, or front wheel fender areas. However, Hyundai Mobis came up with the idea of using the car grille itself as a speaker. This approach not only reduces volume and weight compared to existing products but also lowers costs. Since the speaker is exposed externally, sound transmission to the outside is improved.

Unlike internal combustion engine vehicles, electric vehicles do not require grilles to cool the heat generated inside the vehicle because there is no fuel combustion process. Therefore, electric vehicle grilles are sealed, and separate thermal management devices are attached to the battery. Hyundai Mobis developed technology to utilize the sealed grille of electric vehicles as a speaker. Although this technology, developed in 2020, has not yet been applied to mass-produced vehicles, considering that the typical new car development cycle is five years, it is highly likely to be installed in Hyundai and Kia new models scheduled for release around 2025.