Electric motors are very quiet, which is a good thing for passengers and a bad thing for engineers.
Without the typical sounds of an internal combustion engines, a whole chorus or wind and tire noises reach vehicle occupants' ears.
The 2014 Cadillac ELR presented another challenge. When its gasoline range-extender is operating, it creates low-frequency structure-born vibrations.
"These generally aren't regarded as premium-level sounds," Doug Koons, lead noise and vibration engineer on the ELR, said.
To avoid exposing customers to sounds that are below their social station, Koons and his colleagues employed active noise cancellation. This technology uses microphones placed throughout the cabin and real-time engine data to track undesirable sounds. The car's audio system then plays back opposing sounds to cancel them out.
Cadillac says this approach not only drowns out the buzzing of the ELR's engine, but also saves weight by cutting the amount of sound-deadening material needed to create a tranquil cabin.
Acura offers a similar active noise cancellation system on several of its cars, including the full-size RLX sedan and the entry-level ILX.
In addition to the new-fangled tech, the ELR has triple-sealed doors, thicker glass, and a variety of physical sound deadening materials.
The powertrain all of those things muffle is a modified version of the one used in the Chevrolet Volt, consisting of a 1.4-liter four-cylinder engine, electric motor, and 16.5-kilowatt hour lithium-ion battery pack. However, the ELR produces 207 horsepower, more than the Volt's 149 hp.
The ELR goes on sale in January 2014, with a starting price of $75,995, including destination.