Stereo sound recording in a Volkswagen
Stereo sound recording in a Volkswagen
Stereo sound recording in a Volkswagen
Stereo sound recording in a Volkswagen

In search of the perfect electric sound.

In search of the perfect electric sound.

Text from Phillip Bittner
Images from Volkswagen Aktiengesellschaft

January 2019

From July 2019, the installation of a warning sound generator will be compulsory for electric cars. But how should an electric car sound to ensure that it is perceived both safely and agreeably by other road users? A visit to the e-sound experts at Volkswagen.

It is loud on the acoustic exterior measuring track at the Volkswagen factory in Wolfsburg. This is not due to passing cars, however, but rather to the neighbouring wildlife. Numerous geese are taking a break at the process water holding reservoir immediately adjacent to the approx. 600-metre-long exhibition grounds on their way south and are chattering for all they’re worth. “It wouldn’t be so easy to measure now,” says Dr Ingo Hapke, head of the acoustics team at Volkswagen, laughing. A good job that everything is already wrapped up or on the hard drives of the measuring computer today and the prototype of the ID. Neo, appearing at the end of 2019, is sitting peacefully under its tarpaulin.

Only a short time ago, the future member of the electrified ID. family had been performing countless laps. Again and again, the acoustics experts drove the electric vehicle through the acoustic measuring point, which – equipped with several stand microphones – is located in the middle of the track. Not silently like today’s electric vehicles, however, but rather with a sound that is still a secret but that will accompany the ID later.

 

New electric sound through EU regulation.

The reason for this is a new EU regulation that will come into force from 1 July 2019. It stipulates that an acoustic vehicle alerting system, AVAS for short, must be installed in new types of hybrid electric and purely electric vehicles to protect other road users. There are numerous specifications. The “continuous sound”, as it is worded in the legal text, must depend on the speed. Pedestrians or cyclists should thus be able to recognise, based on the sound of the electric car, whether the vehicle is accelerating or braking. When reversing, a continuous noise is sufficient. The EU regulation also defines the volume of the sound at different distances from the vehicle, but also the frequency shifts it may have. From 20 kilometres per hour, the volume (level) is slowly lowered because then the rolling noise of the tyres is loud enough that an additional acoustic signal is no longer required.

The new EU legislation presents exciting challenges for Hapke and his team. “We want to generate as much sound as required by law externally and as little as possible in the interior of the vehicle,” says Hapke. This can be achieved on the one hand by the positioning of the speaker system, which is as far outside as possible, and on the other hand, by decoupling the speaker from the body. “Sound is not only transmitted through the air, but also via objects,” explains the expert. The EU requirements will also restrict the sound spectrum. “A piece of music or the sound of horses’ hooves aren’t allowed,” says Hapke.