When auto manufacturers set out to create award-winning vehicles, much consideration is given to interior sound quality. Ironically, the manufacturers have been so successful in mitigating road noise they have inadvertently caused a new problem for themselves: Apparently, the cars are too quiet.

Noise levels inside the vehicle’s cabin are affected by everything, from obvious sources such as engine, transmission, and exhaust to the not-so-obvious—such as the seat adjustment motor.

As reported by The Wall Street Journal, “Ten years ago most interior noises couldn’t even be heard because of the engine and road noise,” says John Tepas, vice president of engineering at Mahle Behr Troy, the Michigan-based subsidiary of Mahle GmbH, an auto-parts maker that produces such components as heating, air-conditioning, and ventilation systems. Recent progress in damping those sounds, he says, has forced manufacturers to lower noise levels “even on little parts like the tiny motor that runs the vent door that opens and closes in a heater.”

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