Those who watched the Super Bowl must have seen Genesis’ ad spot featuring its long-awaited GV80 SUV. More than the matte or metallic paint finish, what’s really interesting about it lies under the hood. Developed by Analog Devices Inc. (ADI), the Automotive Audio Bus (A2B) technology is claimed to deliver superior audio quality while reducing the cabling, the weight, as well as the design complexity and overall cost.

“Over the last eight to nine years, our focus, in addition to our engagement to our traditional tier-one customers like Continental, has been to work with OEMs like Hyundai,” Vlad Bulavsky, product line director, automotive connectivity and sensing, Analog Devices, told EE Times. “We want to know and understand the pain points, the challenges that OEMs have in order to move their technology forward and satisfy customers when driving their car.”

Hyundai Motor Co. said it plans to adopt ADI’s audio bus for its road active noise control (RANC) systems as well as audio connectivity and infotainment applications.

Cabling weight down 75%

Vehicle interior noise primarily comes from three sources: the powertrain, the road and the wind. Looking ahead, in-cabin quietness will become a distinguishing feature as more and more electric vehicles hit the roads. “Electric vehicles and plug-in hybrid electric vehicles don’t have engine noise, and the road noise that comes out of the tires against the asphalt is becoming tiresome,” said Bulavsky. Road noise reduction is imperative to ensure a serene driving experience in future vehicles.

After 6 years of research and development, Hyundai late in 2019 unveiled its RANC system to dramatically reduce noise within the car cabin. Using an acceleration sensor, RANC calculates the vibration from the road to the car, and the control computer analyzes road noise. Computation and signal transfer speeds are optimized, making it possible to analyze in 0.002 second the noise and produce an inverted soundwave, generated by the DSP. Based on tests evaluating road surface, vehicle speed, and different seating positions, Hyundai claimed its RANC system could reduce in-cabin noise by 3dB.

Hyundai-Road-Noise-Cancellation-System

Hyundai Motor’s first road active noise control system, RANC (Image: Hyundai)

ADI and Hyundai collaborated to architect the all-digital RANC system and connect remote sensors in a daisy chain sequence to the central processing unit. Here, the A2B technology enables connectivity to microphones and vibration sensing systems. What’s important for OEMs, said Bulavsky, is not just to look whether it makes more sense to connect them in a daisy chain or point-to-point. “The fundamental advantage of A2B is also the single-sample latency.”

ADI claims its A2B technology ensures simultaneous sampling and delivery of data on all system nodes for each frame. “It is basically a master-slave node configuration where the data is being sampled exactly at the same time and exactly at the same place. That’s why you are getting just a single-sample latency.”

In the case of technologies like Ethernet EVB, he continued, “you can achieve the same function, but you have much more latency because you have to reassemble your packets [of data] and do some processing. The same way you have I²S for chip-to-chip, here we have I²S from one node to another node.”

Until now, ADI claims, the use of road noise cancellation systems in cars failed due to high costs. “That would be impossible,” Bulavsky outlined. “The only way that you can achieve the same latency is by using analog technology, but analog cables are too heavy, too costly and difficult to implement.”

The A2B technology reduces cabling weight by up to 75 percent and improves automotive fuel efficiency and total system costs, said Bulavky. “We took a typical example of connectivity between the head unit and amplifier, so what used to be served by analog cabling.” Here, “you can reduce the number of separate coax cables to a single A-to-B cable that is capable of doing exactly the same.”

Improving bandwidth

Beyond road noise cancellation, ADI stresses that its A2B technology is suitable for transporting digital audio and delivers superior audio quality, opening new opportunities for audio connectivity and in-vehicle infotainment applications.

The Norwood-based company is working “on improving the delivery over the bus and increasing the bandwidth of the bus” to expand the use cases, said Bulavsky. “Right now, it is primarily a connectivity between a head unit and an amplifier, but we really want to expand the use cases to our different submodules or to different parts of the infotainment system requiring audio, voice or acoustics.” For that, ADI is engaged with OEMs to include its A2B technology in applications such as personal audio zones, microphone arrays for hands-free, in-car communications, self-parking systems, and autonomous driving systems.

So far, ADI has shipped more than 15 millions A2B nodes. “We are on the road with 14 out of 20 OEMs,” including Ford, Hyundai and BYD.