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Engine noise (red) is canceled by opposing sound waves (blue) generated by Bose software.

Bose, NXP team up to hush powertrains

Bose has teamed up with NXP Semiconductors to offer its noise-management capabilities to automakers so they can implement Bose Active Sound Management technology on vehicles that don’t have Bose speakers and amplifiers. The software is said to lower powertrain sounds by as much as 20 dB.

The push to improve fuel economy is among the factors prompting automakers to look at noise cancellation as a way to reduce powertrain noise. Higher-revving four-cylinder engines, lighter bodies, and less noise-reducing materials make noise management more challenging, especially in smaller cars.

“High-efficiency four cylinder engines tend to be noisy, which can impact consumer’s perceptions of vehicle quality,” said Martin Dluzansky, Senior Business Development Marketing Manager at Bose Automotive Systems Division. “Automakers want to migrate noise cancellation down to mainstream vehicles. If they can eliminate some noise-deadening techniques and eliminate some sounds that are considered very negatively, they can make the car lighter and still improve the perception of quality.”

Bose already provides noise cancellation for higher-end vehicles that use Bose hardware. The partnership with NXP, which is not exclusive, was made to expand the market.

“Active sound management is already being used,” Dluzansky said. “What we’re doing now is to decouple it from Bose systems so anyone can use it. We partnered with NXP because their chips are widely used in radio head units.”

The noise cancellation does not use the same technology familiar to fliers and others who use noise-canceling headphones. Headphones use techniques that cancel a wide range of frequencies in a very small area. Cancellation techniques for the entire cabin focus on specific frequencies.

“We use adaptive feed forward, which lets us cancel a narrow frequency range in a large area,” said Seiji Kawakami, Global Manager for Bose Active Sound Management. “With feed forward, you don’t have to account for the seat position or other varying conditions. We’re looking at long sound waves, so there’s very little difference where you’re sitting inside the car.”

The system uses information from cabin-mounted microphones and engine information from the vehicle’s network. A Bose algorithm monitors and measures noise, sending acoustically opposite sound signals through the vehicle’s speakers to cancel targeted noise. Bose engineering specialists will help automotive engineers tune the system for each vehicle and for different engines.

“Car companies aren’t looking for the maximum cancellation, they want sounds to stay at the same levels,” Kawakami said. “They want linearity for the powertrain sound peaks and dips. Noise cancellation needs meet the powertrain requirements for each type of car. Additionally, each type of engine will have different tonal qualities.”

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