This has to do with the drivetrain of the car. In simpler terms, the power delivery system of the car. A 2wd or a two wheel drive is any general stick shift(manual transmission) car you drive. Either the front two rotates and pull your car or the back two rotates and push your car forward. For a 4wd or a four wheel drive, you can switch to all of the wheels being driven. Provides better grip on the road.
How the system works. Active Noise Cancellation (ANC) is designed to dramatically reduce low frequency noise in the interior. The system operates whenever the car is running, regardless of whether the audio system is on or off. There are two microphones in the cabin area.
Installing insulation is one way. Limiting the transmission of sound from one area to another requires a material that encloses the source of the noise, forming a barrier between the source and the adjacent areas. This is exactly how insulation works! There are two types of noises: airborne and impact.