BMW engineers have developed a technique for changing the way a driver perceives engine noise, which is sophisticated enough make a diesel engined car sound like it is powered by a high-revving petrol unit.
BMW engineers have built two experimental prototypes, a 635d and a Mini Clubman with the option of four different engine notes including one that sound to its occupants like an old-fashioned ‘muscle car’ V8 engine.
You can hear the system at work in the video below.
The company says that the technique dubbed ‘Active Sound Design’ and utilizing the car’s own sound-system is so effective that test drivers in vehicles equipped with the set-up perceived their cars to be performing better than standard test vehicles with identical performance.
The prototype is based on 635d, which has been treated to BMW’s new ‘acoustic lightweight construction’ techniques, which uses new lightweight sound and vibration deadening materials in the engine bay and under the car.
In addition, says BMW, the engine is "partially encompassed by an acoustic capsule". All of which greatly reduce the noise emitted by the engine into the cabin.
The upshot is that with the car’s natural engine note nearly completely subdued, a new, artificial, engine noise can be fed to the occupant’s ears via the audio system.
According to Albert Kaltenhauser, BMW’s Manager for Airborne Sound, Acoustics and Vibration, BMW started work on the system to improve the sound characteristics of diesel engines.
"Today's diesel engines are capable of a lot. They're efficient, highly effective and high-torque, but until now they were lacking the right sound," said Kaltenhauser. "With Active Sound Design, they're finally achieving the sound that they deserve based on their performance characteristics."
BMW says that Active Sound Design allows for "significantly more systematic and finer adjustments than classic sound design, which is oriented around the intake and exhaust systems."
"Even minimal changes to vehicle sound can have a big impact, since human hearing subconsciously evaluates acoustic surroundings like a high-performance analyser and all changes are continuously registered in the brain," said Kaltenhauser.