Last month, BMW introduced their latest innovation to graduate from their Research and Development Center: BMW Active Sound. BMW engineers developed a technology that changes the way a driver perceives engine noise.

Presented in a MINI prototype for petrol engines in 2009, Active Sound Design now also helps diesel engines achieve a sporty sound that wasn’t possible for this type of engine until now. The sporty performance characteristics of modern diesel engines and their high torque, especially when starting up and accelerating, contradict the acoustic sensation of diesel vehicles.

Harsh ignition impulses during combustion, which are inherent to diesel engines’ function, are responsible for their characteristic noises — commonly referred to as “knocking”. This undesirable acoustic characteristic of diesel engines has been brought to a very low level at the BMW Group through intelligent acoustic lightweight construction. This makes room for Active Sound Design, which supports a sporty sound quality. It makes outstanding driving performance audible.

In order to have a special audio experience and for a diesel vehicle to sound really sporty, sound designers have to optimally adjust the sound to the vehicle and its engine performance. Too much sound with too little engine power would make a negative impression. The engine sound must constantly provide for a harmonious driving experience. The particular challenge is allocating the right dosage of sound in all driving situations and creating an authentic audio character. An active system allows for significantly more systematic and finer adjustments than classic sound design, which is oriented on the intake or exhaust system.

The other experimental prototype built by BMW was a 635d witth the option of four different engine notes including one that sound to its occupants like an old-fashioned ‘muscle car’ V8 engine.
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.

To demonstrate the BMW Active Sound technology, the folks over at Autocar took a ride in the experimental-prototype MINI Clubman with a V8 diesel engine noise. Let’s have a look!

[Source: Autocar | BMW ]