If you’re Audi and known for high-performance vehicles such as the R8 – and their attention-getting exhaust notes – then how do you add a signature sound to the otherwise silent electric version of the vehicle, the R8 e-tron?  And also make sure that pedestrians and others will hear the vehicle coming, as required by federal law, and that enthusiasts will hear it before they see it, as required for sports cars?

The solution for Audi is called e-sound. While other electric vehicles make sounds such as the NissanLeaf’ssci-fi-style sound effects and the VolkswagenE-Golf'sWookie-like warble, Audi wanted more of a performance-oriented​ guttural growl for the R8 e-tron. The task was assigned to Audi acoustics engineer and amateur musician Rudolf Halbmeir to compose an appropriate soundtrack that’s coordinated with gas-pedal pressure.

Halbmeir  and his colleagues typically tune aspects of a combustion engine to hit on an exact exhaust note. But Audi admits that the high frequencies generated by the e-tron’s electric motor “are not exactly melodious”  So a “synthetic sound signature” was developed using computers and software to mix sounds, listen and then remix them, more like a record producer than an automotive engineer.

That was fine with Halbmeir, who writes songs, plays several instruments and composes music in his personal recording studio. "There aren't many differences between music and a vehicle's sound," Halbmeir said in a press release. “I trust my instincts and have to try out new ideas to determine where they will take me."

Some of those ideas came from science-fiction films because “there was nothing in the real world which offered quite the right sound, "Halbmeir said. But fitting with Audi’s "Truth in Engineering" credo, the sound also had to be mechanically inclined. "Data relating to the electric motor's rotational speed, vehicle speed, loads and other parameters is continuously supplied by the vehicle to the control unit,” added Audi’s Lars Hinrichsen in the release. “It then uses this data to generate sound." Kind of like the pioneering German industrial-rock band Kraftwerk.

The e-sound wafts from a rugged loudspeaker attached to the car's undercarriage. "We designed it to handle as much as 40 watts, said Audi’s Axel Brombach. “But during normal operation it ranges between five and eight watts. That's loud enough for nearby pedestrians and cyclists to hear the e-tron." As long as someone isn’t drowning it out with a bumpin’ 1,000-watt aftermarket system.

Audi says that only “a fraction of the sound signature enters the vehicle's interior." As for why the e-sound isn’t piped into the interior to give the driver more feedback, Audi says the “e-tron models call for an atmosphere of calm, which best conveys the unique experience of electric driving."

They could always add something like BMW’s Active Sound Design on the M5 that “reproduces the car's engine sound via the in-car audio system.”

[Source: Autoblog]