There are many ways of making a vehicle more fuel efficient. Improvements in engine technology, materials, rolling resistance and aerodynamics can all contribute towards making a car easier on gas than its predecessor.
How about making it quieter?
You may think making a car quieter at speed might involve more sound-damping material and therefore more weight, but General Motors has used techniques often found in sound-cancelling headphones improve the economy of the Chevrolet Equinox.
Engines are generally most efficient at quite low engine speeds, but this can often result in unpleasant "boom", or low-frequency noise that resonates through the car at lower revs and under load.
To deal with this, GM uses Active Noise Cancellation. At lower engine speeds, between 1,000-1,500 RPM, a noise-cancelling module kicks in that creates a sound to cancel out the unwelcome boom, making it inaudible to the driver.
The other background noise found in cars such as wind noise, road noise, stereo sounds and passengers made finding the right balance difficult, but by linking the artificial sound with the engine's firing frequency, the team was able to solve the problem.
The end result? The four-cylinder Equinox manages 32 miles per gallon on the highway, a touch better than the 2011 Ford Escape Hybrid at 31 MPG highway.
Better fuel efficiency and a quieter car? Maybe you can have your cake and eat it.
[GM via All Car Tech]