All electric vehicles, but also plug-in hybrid ones must use a warning sound generator, according to a new EU Directive, in force starting 1st of July 2019. The measure also targets hybrid and fuel cell models, regardless of the body style.
Cars, trucks and buses with electric, hybrid or fuel cell propulsion must use the Acoustic Vehicle Alerting System (AVAS) in order to protect other road users that might not hear the vehicles driving at low speeds. The system must remain active up to a speed of 20 km/h. The EU Directive formulates the parameters for how such a warning system 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 experts in acoustics at the Mercedes-Benz Technology in Sindelfingen work on developing and implementing what they call the e-sound, individually configured for each electric Mercedes-Benz model. They mount special microphones on the exterior of the cars, after carrying out simulations, measurements and evaluations.
The development stage also involves test drives with a particularly sensitive passenger, the artificial head. It registers the tiniest noises and comes impressively close to the human hearing.
The sounds allowed for road use in Europe differ slightly from those especially designed for Japan and China, as regulation are different in terms of volume and activation. Thus, the stationary vehicle must already generate a sound when a gear is engaged, becoming louder up to 30 km/h. drivers are not allowed tu switch off the AVAS in almost all countries.