The Sound of Music....Not Quite !

Now it's law to have sound generation fitted to new EVs. Since 1 July 2019, it has been mandatory to install a warning sound generator in electric cars. This is due to a new EU Directive. This stipulates that initially in newly certificated hybrid, electric and fuel cell vehicles - also trucks and buses - the Acoustic Vehicle Alerting System (AVAS) must be installed for the protection of other road users. In the EU the acoustic warning is mandatory up to a speed of 20 km/h. The Directive formulates the parameters for how an AVAS warning may and may not sound in great detail. This applies for example to the minimum and maximum sound volume, and to certain sound components.

The exterior noise testing facility at the Mercedes-Benz Technology Centre (MTC) in Sindelfingen: the futuristic-looking room is clad with sound-absorbing material. This is where special microphones are used to create an individually configured e-sound for each electric model. Simulations, measurements, evaluations and detailed improvements continue until the result is perfect.

An example of the way manufacturers are working on this relatively new part of the business is Mercedes. The sound experts of the acoustic test facility at the Mercedes-Benz Technology Centre (MTC) in Sindelfingen are working on giving a voice to the electrified Mercedes. Special microphones in the exterior sound testing facilities are used to develop an individually configured e-sound for each electric model. Simulations, measurements, evaluations and detailed improvements continue until the result is perfect. During the subsequent test drives, there is a particularly sensitive passenger on board – the artificial head. This registers the tiniest noises, and comes impressively close to human hearing.

Different standards in different markets

The Mercedes-Benz AVAS sound differs only slightly for the EU, Japan and China. There are other requirements for the USA, for example concerning the sound volume. Furthermore, the stationary vehicle must already generate a sound when a gear is engaged, becoming louder up to 30 km/h. Switching off the AVAS by the customer is prohibited in almost all countries.