Most people are familiar with noise canceling headphones, but now GMC has taken that technology and upsized it into a version that can make an entire vehicle quieter. What's really different however, is that GMC is using the noise canceling system to give the Terrain SUV better fuel mileage, not just to add refinement.
Engineers were tweaking the Terrain's six speed transmission's shift points, and found that keeping the engine running at lower revs would improve the gas mileage. While the uptick in mileage was exactly what they were after, the lower engine speeds resulted in an objectionable low frequency boom in the cabin from the low revving 4 cylinder engine. By adding the active noise reduction system, they were able to keep the fuel saving tweaks without making the ride too noisy.
The system uses two microphones embedded in the headliner to detect the boom, then pumps an out of phase signal to the car's speakers to cancel out the noise.
The system is standard equipment on 2011 Terrains equipped with the 2.4-liter Ecotec engine.