Noise cancellation: The sounds of silence in the car

October 24, 2014 // By Christoph Hammerschmidt
Infotainment system vendor Harman has succeeded in applying noise cancellation technology, hitherto known mostly from headphones to the interior of cars: The company's Road Noise Cancellation (RNC) noise management solution, jointly developed with British sports cars legend Lotus Engineering, minimises noise generated by the contact of the tires with the road surface.

RNC, currently on its way to market introduction, will not only ensure a more comfortable while more quiet driving experience. The technology also has a strong economic aspect: It enables carmakers to use lighter weight materials and improve fuel economy without compromising vehicle noise levels.

In pursuing ways to lessen the environmental impact of vehicles and raise fuel efficiency, car designers are reducing vehicle weight, often by using less noise-dampening insulation in the car's interior. The use of lighter materials, however, increases perceptible road noise inside the vehicle, which then penetrates the interior (and passenger ears) and also compromises the audio experience of the on-board infotainment system. Traditional NVH (Noise, Vibration, and Harshness) methods have difficulties mitigating these issues satisfactorily, and these technologies also tend to add weight, which cancels out the fuel economy effect of using lighter materials.

With the latest Harman solution, drivers and passengers can soon look forward to a quieter ride. The Harman HALOsonic noise management suite comprises a Road Noise Cancellation solution (RNC) which detects and neutralizes unwanted road noise, and thereby creates opportunities to improve vehicle weight and handling without impacting interior noise levels.

Being the first solution of its kind in the industry, RNC is based on the principle of using “anti-noise” to counteract road noise. To implement RNC, the chassis of the vehicle is fitted with accelerometers which enable the system to measure correlation of vibration coming from the road and the resulting noise inside the cabin. Subsequently, Harman's algorithm in the controller creates inverse sound waves through the car’s audio system loudspeakers to cancel out the noise caused by the road-induced vibration. It is also able to cope with the broadband nature of road noise, with its wide range of frequencies. The solution at hand can reduce the peaks of the noise across the target frequency range, creating a quieter experience within the vehicle cabin.

HALOsonic consists of a suite of