Hisses, purrs and roars: how good car sounds are made

By dpa | 24 January 2018


MUNICH: V8s bubble lushly and turbo-engines chirp when exhaust-gas pressure is released.

BMW uses specially tuned exhaust-gas systems for every vehicle type in order to generate particular acoustic effects. “The interpretation should sound comfortable in the lower speed range, and energetic, dynamic and sporty in the middle and upper speed ranges,” says Christian Stempel, the head of sound design and aeroacoustics at BMW.

The co-ordination of the combustion engine in combination with this creates the basis for the sound of the exhaust. “A good engine sound stands out by balancing all sounds sources, including the intake and exhaust openings as well as engine mechanics,” says Michael Pfadenhauser, the head of vibrations and acoustics at Porsche.

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Sound engineers set their own focus for every model, including one characteristic that’s typical of the manufacturer. “The engine sounds deliver acoustic feedback on the vehicle’s performance capabilities — and at an emotional level to boot.”

Sound development already starts in the the initial phases with simulations, long before the first prototypes are available. “With the help of simulations, the sound of the intake and exhaust openings can be calculated and made audible,” says Pfadenhauer. “The first prototypes of the exhaust and intake systems are built off the basis of this and their sound assessed with real vehicles.”

Characteristics and intensity matter here depending on the driving situation. “A comfortable ride should be possible with low loads and speeds,” he says. Intensive feedback on this sound allows for the performance of this vehicle to be experienced for more dynamic rides with higher loads and speeds.

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In order so that occupants can experience the motor and exhaust sounds without annoying other drivers, so-called “sound symposers” transmit the sound of the intake noises inside. An artificial sound is generated by stimulating the body structure via an electric converter or with the support of the audio system.

For older cars, a sports exhaust system is the easiest way to change these tones. A sports muffler, or alternatively an exhaust system silencer, is an inexpensive way to retro-fit these vehicles, said Harald Schmidtke, the head of Germany’s Association of Automobile Tuners. The complete system is the variant with more sound possibilities.

The subsequent installation of so-called “sound actuators” likewise changes the tone. These active sound boosters contain a control unit and sound actuators in which special loudspeakers generate a certain exhaust sound.

Vincenzo Luca of leading technical inspection association Tuv recommends vehicle owners also pay attention to a correct installation. Special attention must be paid to low-lying vehicles, as these parts can easily scrape off the ground.

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