http://eandt.theiet.org/news/2015/nov/ford.cfm
Ford has developed a sound cancelling system for cars to give drivers quieter journeys. The system, called Active Noise Control, uses three microphones that are placed in the cabin to detect noises produced by the vehicle, such as from the engine and transmission systems. Opposing sound waves are then broadcast from the audio system to counteract these in a similar fashion to noise-cancelling headphones.