Link:

http://media.gm.ca/content/media/ca/en/gm/news.detail.html/content/Pages/news/ca/en/2011/Sep/0909_Equinox

Science of Sound in Chevy Equinox Saves Cash at the Pump

Oshawa, Ontario (September 9, 2011) – General Motors engineers borrowed from stereo headphone technology to help give the Chevrolet Equinox segment-leading fuel efficiency.

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 a segment-best, 6.1 L/100km highway fuel consumption, better than segment competitors Honda CR-V (7.1 L/100km), Toyota RAV4 (6.9 L/100km) and even the Ford Escape Hybrid (6.5 L/100km).

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 efficiency. 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 helped improved fuel efficiency.

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

isn't this old news?

Huh?

It is old news, but still cool to read. Even though in real world use almost nobody is getting the advertised mileage.

It is old news, but still cool to read. Even though in real world use almost nobody is getting the advertised mileage.

We had a rental Equinox AWD 4 Cylinder at work last year and it gets far better milage than the 4 cylinder Escape. It was averaging 8.5 L/100 mostly hwy as opposed to the Escape at 9.5 L/100.