Molex recently introduced a new accelerometer-based Road Noise Canceling (RNC) sensor. It is the first product of a new line of Active Noise Cancelation (ANC) sensors for automobiles. The sensors are designed to decrease common car noises caused by the road, wind, and HVAC systems. But perhaps more importantly, the ANC technology can reduce low-frequency sounds that can cause driver fatigue.
The new ANC technology is in response to the anticipated trend of electric vehicles. Molex surveyed 230 auto manufacturing decision makers to create a vehicle forecast for 2030. The results overwhelmingly supported the development of electric vehicles. The survey results predict that 90 percent of new cars in 2030 will be electric.
ANC technology is more important for electric vehicles because their motors are much quieter than combustion engines. “As the transition to electrified vehicles intensifies, it will become critical to reduce road noise, which today is masked by internal combustion engines,” explained Carrieanne Piccard, VP and general manager of the Molex Transportation Solutions Business Unit.
In the past, road noise was dampened by installing heavy sound-absorbing materials to insulate the car from unwanted noise. But today, ANC technology is more common. It works by broadcasting cancellation wave forms from the vehicle’s speakers to cancel out constant or predictable noises.
The frequency of the unwanted noise is detected by placing a sensor wherever the noise vibrations are created. For example, a common noise is the sound of tires rolling on the road surface. Tire noise is reduced by the tire design, materials and pressure. The sounds that are produced can be canceled by mounting a sensor on the subframe near the suspension points, where the noise originates, and creating a cancellation wave to cancel the vibrations detected. What really sets the new RNC sensors apart from the competition is their ability to cancel vibrations at very low speeds.
A limiting factor of ANC technology is the ability to sense vibrations and to do so quickly enough to create a wave to cancel the sound. It can take as little as 0.009 seconds for vehicle noise to reach our ears. To create RNC sensors that can react to vibrations that quickly, Molex collaborated with Analog Devices to incorporate its Automotive Audio Bus (A2B) technology, which uses low latency networking technology that allows the digital signal to be transferred in under 0.002 seconds.
When tested, Molex found that the RNC sensors were able to remove 90 percent of road noise across a broad band of frequencies (from 20 Hz to 1 kHz). This level of noise reduction can improve driver safety. It eliminates the humming noises from roads that are associated with “highway hypnosis” and driver fatigue.
Molex technology is being adopted by leading automotive suppliers and equipment manufactures. Jaguar and Land Rover have already announced that they will be deploying the technology in their vehicles.