Harman develops Road Noise Cancelation technology

Tyre industry professionals will be very familiar with the tyre label’s role in reducing the noise on European roads. Yet this consumer-facing rating means little to those in the car itself. Now, premium global audio and infotainment group Harman is expanding its HALOsonic suite of noise management solutions, co-developed with Lotus Engineering using patented Active Noise Control Technologies, to achieve an industry first.

Road Noise Cancellation (RNC) technology minimises unwanted noise generated when the vehicle tires roll across the road surface. RNC, which is presently ready for market implementation, enables automakers to use lighter weight materials and improve fuel economy without compromising on vehicle noise levels.

In pursuing ways to lessen the environmental impact of vehicles and raise fuel efficiency, automakers 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. The 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.

The Harman HALOsonic RNC detects and neutralises unwanted road noise, and thereby creates opportunities to improve vehicle weight and handling without impacting interior noise levels. Based on the principle of using “anti-noise” to counteract road noise, 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, the proprietary algorithm in the controller creates inverse sound waves (coming from each speaker) through the car’s audio system 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 HALOsonic RNC solution can reduce the peaks of the noise across the target frequency range, creating a quieter experience within the vehicle cabin, Harman says. The company’s True Audio technology also ensures that only unwanted engine or road noise is cancelled, while preserving music signals in a similar audio range.

Commenting on RNC, Michael Mauser, president of Harman Lifestyle Division, says: “We’re excited to be pioneering these innovative technologies for noise management inside and outside the vehicle with HALOsonic, of which RNC is a key part. An uncompromised sound experience is more important than ever to today’s drivers, and less noise also means drivers are less likely to become tired or distracted. By taking disturbing road noise out of the mix, we can provide automakers with greater opportunities to exploit lightweight materials without the risk that the perception of quality and harmony in the car will be compromised.”

Colin Peachey, group chief engineer -controls and electrical at Lotus Engineering, adds: “Lotus Engineering has many years of experience in developing vehicles, not only for the world renowned Lotus Cars but also its global engineering client base of car companies around the world. Lotus has vast knowledge of both the dynamics and noise performance of chassis systems. Indeed Active Noise control was a spin off technology from when Lotus pioneered active suspension for its Formula One cars in the 1980s and over the years, Lotus has led the way in this field of advanced research and development of technologies for cars of the future.”

HALOsonic consists of a suite of noise management technologies to improve noise levels and to enhance and contour sound inside and outside the vehicle. In addition to RNC, HALOsonic comprises Engine Order Cancelation (EOC) and internal as well as external Electronic Sound Synthesis. External ESS (eESS) generates sound primarily for hybrids and electric vehicles, creating the authentic sounds which drivers and pedestrians are familiar with from combustion engines, thereby increasing safety both for drivers and other road users. Internal ESS (iESS) serves to generate unique sound signatures for vehicles to contour and accentuate the engine sound.