Sounds like green spirit: the e-Golf* engine.

No rattling, humming or roaring: electric cars such as the e-Golf* are quiet – and a potential risk for other road users. Volkswagen engineers have therefore developed characteristic sounds for each e-speed.

*e-Golf: Power consumption in kWh/100 km: 12.7 (combined); CO2 emissions in g/km: 0 (combined); efficiency class: A+

It seems paradoxical at first: for years, engineers have been working toward making cars quieter. Now, they are working on making a sound for noiseless electric engines. The reason for this is that road users also use acoustic impressions to estimate the speed and distance of oncoming cars. However, without an artificial sound, electric cars are scarcely audible and present a risk for road safety. It is, therefore, entirely sensible to equip electric cars with an artificial sound.

According to the NHTSA, the accident risk presented by electric and hybrid cars is 19 percent higher for pedestrians and 38 percent higher for cyclists than that of cars with a combustion engine. After a transition phase, therefore, they will have to be audible for pedestrians up to a speed of 30 kilometers per hour from September 2020. In the EU, new electric and hybrid models will have to emit a warning signal up to a speed of 20 kilometers per hour from July 2019. Then, from July 2021, every newly registered electric vehicle will have to produce a driving noise.

The mix makes the difference

In the search for the perfect sound for the e-Golf, it was decided to use a mixture of combustion engine and electric machine. The sound of a classical engine, after all, is very familiar and easy to identify even in a loud environment. The electric part, on the other hand, highlights the fact that this is a new technology.

During the sound production, the acoustic engineers initially recorded both sounds in a studio. For the electric machine sound, they filtered out unpleasant whistling sounds and added low frequencies. The result is a rich sound with a steady frequency, reminiscent of an intercity express train setting off. The sound of the combustion engine comes from a four-cylinder engine from which the acoustic experts removed the sounds of the generator and the belt drive. Of course, they could also have used a 16-cylinder engine, but the e-Golf is not supposed to sound like a sports car.

A suitable sound for every situation

The acoustic engineers have developed characteristic sounds for every speed. This means that the engine sound can adapt to the rpm of the electric engine. The volume of the e-Golf* therefore depends on its speed. In the car, a sound system brings the synthetic sound to life. The control unit for the system is installed in the radio slot behind the display, while the loudspeakers work in the engine compartment.

When the e-Golf* is stationary, you hear nothing. After driving off, the volume of the e-Sound first increases in a linear manner and then remains constant between ten and 30 kilometers per hour. At higher speeds, it decreases again, and beyond 50 kilometers per hour, the loudspeaker is silent. That’s because, from a speed of 40 kilometers per hour, the rolling noise of the tires takes over the leading role in terms of sound. And the faster the e-Golf* travels, the higher this sound becomes.

Once other road users have got used to the new sound of electromobility, there is no reason not to increase the electric sound component in the future. The e-Golf* could receive any conceivable sound; for example, it could drive around town making the sound of an airplane. But this is rather unlikely. Ultimately, the sound should not only sound like a car but also suit the vehicle. For the e-Golf*, this means one thing above all: remaining environmentally friendly.

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*e-Golf: Power consumption in kWh/100 km: 12.7 (combined); CO2 emissions in g/km: 0 (combined); efficiency class: A+