How Consumer Reports tests cars:

Noise

We evaluate noise as well as measure it. We use precision microphones mounted in the cabin and make digital recordings of sound pressure (known as volume to most of us) while the car is driven over various pavements, including a specially built coarse pavement at our track, and at different speeds. Complementing those findings is noise evaluation conducted by our test engineers during a 30-mile loop on local public roads. They make note of engine, road, and wind noise, and judge the level and quality of the noises, be they raucous or pleasant, annoying or exhilarating.