(September 11, 2011) DETROIT — General Motors engineers borrowed from stereo headphone technology to help give the Chevrolet Equinox segment-leading fuel economy.

Noise and Vibration Development Engineer Jim Vallance and his colleagues at GM’s Milford Proving Ground were tasked with pushing the 2011 Equinox to get 32 mpg on the highway, four mpg better than segment competitors Honda CR-V, Toyota RAV4 and Ford Escape — all rated at 28 mpg.

They knew they could accomplish this if they could run the Equinox engine at a lower RPM and find a way to offset the higher cabin noise levels that resulted. 

“There’s a boom, or very low frequency rumble that comes from the engine when it runs in that RPM range,” said Vallance. “We knew if we could deaden those booms, we could run the engine at the lower RPM, which would provide a significant boost to fuel economy. So we started kicking around ideas and came up with noise cancellation like you see in some high-end stereo headphones.”

Vallance and his colleagues created an Active Noise Cancellation module that detects when the engine is running in the 1,000 – 1,500 RPM range. This engine speed triggers the module to create a sound-killing countermeasure through the vehicle speakers, essentially eliminating the unwanted sound.

Adapting noise cancellation technology to work in a vehicle interior was difficult. High levels of ambient noise from the road, stereo system and occupant conversations posed challenges that required a surgical approach to noise cancellation.

“We take a proactive approach and target only the unwanted sound in the vehicle, which in this case is linked with the engine firing frequency. Then we eliminate it,” said Vallance.

Vallance is a second-generation GM engineer with a patent and other innovations under his belt. He characterizes Active Noise Cancellation as a “bold step taken late in development” that improved fuel efficiency by up to one mpg.

Active Noise Cancellation is standard on the Equinox with a 4-cylinder engine.