November 2018 Issue

Eye On Electronics

Vehicle audio system capabilities are advancing rapidly. If a customer complains that his vehicle is making ‘a strange noise,’ the source may be inside rather than outside.

Complexity begets complexity. As vehicles offer more driver and safety assists, there are more warnings for a driver to receive, digest and act on. A new contender for intelligent notifications is the seat-centric audio system, meaning two or three speakers placed in the headrests or headliner that direct audio at specific occupants only.

Using digital signal processors, the sound can appear to be coming from the left, right, ahead or behind, or a combination of directions. It can be shaped so the message might appear to be coming from far away or up close. For example, the navigation prompt, “Prepare to turn left in 1 mile” would sound distant and feed primarily in the left ear. A follow-up, “Turn left in 100 feet,” might be louder, more urgent, sound closer and clearly be on the left side. That’s for the driver.

Passengers could take advantage of “individual sound zones,” as infotainment supplier Harman International calls them. Bose talks of “sound placement.” Front-seat passengers wouldn’t hear what’s going to the second or third rows. An occupant of the second-row left or right seat wouldn’t hear what the other passenger in that row hears, allowing multiple video sources in back with no need for each person to wear headphones.

Automotive audio engineers also shape the sound of the vehicle’s engine to make it sound sportier in some models, quieter in others. They also implement active noise cancellation to reduce the need for additional sound-damping material. Sound-shaping is especially important to make clear that advanced driver-assist systems, or ADAS, promote safety, not complexity.

John Pelliccio, head of product communications for Bose Automotive Systems, said, “For drivers, you can make a sound [spoken instruction] louder, have a sense of urgency or control the direction and distance of the sound.” Bose and Harman are two of the largest audio companies that help automakers develop infotainment systems, and now systems that communicate with the driver.

Before there was shaped sound or sound placement, there were already at least four ways to alert the driver about potential hazards:

Audio alerts, typically beeps or tones that can be heard throughout the vehicle, are the most common. Sometimes the speakers emulate an existing sound, such as rumbling when the vehicle crosses onto a lane divider even if it’s not raised or grooved. Many drivers dislike beeps because all the warnings seem to sound alike. Also, some beeps are high-pitched, and older drivers may not hear them.

Visual alerts use lights to notify the driver. An escalated alert may go from solid to flashing, or it may change color. For blind spot detection, a light may be in the side mirror or A-pillar, solid when a vehicle is in the blind spot, flashing if you try to change lanes at that time. Warning indicators may be in the instrument panel and/or the head-up display. A handful of automakers such as Genesis, Hyundai and Mazda put blind spot detection indicators in the head-up display; many others do it with lane departure warnings and the new GMC Sierra does it especially well because of its large HUD. Urgent warnings such as “Brake Now” may be a half-dozen red diodes flashing off the bottom of the windshield.

Haptic alerts through the steering wheel. The steering wheel vibrates to warn the driver of a lane departure or blind spot issue. Some automakers have low-medium-high settings, where low is almost unnoticeable. Some critics say unskilled drivers may be frightened by a vibrating steering wheel, although it’s unclear how much of this is anecdotal. The vibrations are typically a higher, constant frequency than the kind of vibration you get from, say, a rough road or a steering problem.

Bose notes that as self-driving vehicles proliferate, a steering-wheel shaker won't be useful if the driver doesn’t have his or her hands on the wheel.

Haptic alerts through the driver’s seat. The left and right seat bolsters vibrate to indicate an issue on the left or right. Both bolsters vibrate if you get too close to something in front or in back. General Motors, with its Safety Alert Seat, is the primary proponent of this haptic alert system. While haptic steering wheel feedback could be made directional (left or right), all of GM’s Safety Alert Seats work that way.

Either kind of haptic feedback is better than today’s nondirectional sound alerts because passengers often can’t resist commenting on the driver’s apparent lack of prowess when the vehicle crosses the lane boundary again. More than a few drivers will turn off lane departure warning or blind spot detection rather than listen to passengers gripe. That’s why focused sound heard only by the driver has such promise.

Gamers already use 3D sound effects to mark the sound of a spacecraft flying past, or a rifle shot and a ricochet. And it worked for surround sound home theater systems when a jet plane flew through the sound field in the 1980s film Top Gun.

In a vehicle, sound delivery can be more complex. Chris Trestain, a user experience team manager for Harman, said, “In a headphone, the speaker-to-person’s-ear distance never changes. The time of arrival [of sound] never changes. In a vehicle, we have to come up with solutions that are more robust. We have people of different sizes, people leaning all over the car. We have to make it a larger sweet spot. We have a different algorithm that looks to all the [factors] and comes up with the best options…of different filter combinations that cancel out [unwanted] low-frequency sounds.” High-frequency sounds are less likely to bounce off windows or doors and create unwanted sound paths to the ear.

Creating a realistic sound field for each seat in the vehicle requires two or three speakers, or as many as a dozen speakers for four people in the first and second rows. That means the speakers also must be small and light.

Bose resurrected the speakers-in-headrest solution that dates back decades to when cars were noisier. They have speakers for both passengers in the Mazda MX-5 (Miata) from 2016 on, and now in the driver headrest of the 2018 Nissan Kicks. The UltraNearfield speakers in the Kicks can be adjusted to direct sound only at the driver or widened to create a more immersive experience for all. The same speakers plus more electronics and a digital signal processor could create a Bose Sound Placement system for the driver.

“If navigation tells you to turn left in a mile, we can have that sound come from virtually far in front of you and to the left,” said Bose’s Pelliccio. “As you get closer to the turn, and the prompt says ‘Turn left in 50 feet,’ we can have that come much closer to your face and to the left, so closeness of the sound indicates urgency.”

According to GfK, Germany’s largest market researcher, localized audio cues were seen by participants as less distracting and more readily noticed than visual cues. Melinda Jamil, senior research director for user experience at GfK, says drivers perceive as many as 10 advantages with focused audio cues (but note this was research done on behalf of a client already headed in that direction):

•Improved focus (because of localization of sound).

•The ability to multitask (because of separation of sound).

•Better situational awareness.

•Faster response/reaction times.

•Less need to take eyes off road to view display prompts.

•More intuitive reactions requiring less concentration.

•Greater passenger awareness.

•An enhanced input when visibility is limited.

•Optimized sound placement for the hearing-impaired.

•Enhanced audio experience and the “cool” factor.

Meanwhile, automakers continue to add speakers to their high-end vehicles for buyers who may equate speaker count with quality. The Cadillac CT-6 Panaray system has 34 Bose speakers. With Harman, the Lexus LS Mark Levinson 3D system has 23 speakers driven by a 16-channel amplifier while the Lincoln Navigator and Continental have 20 speakers each and a 20-channel amp. With that many speakers, they can also be used for automatic noise cancellation, or for enhancing engine sounds, especially when those engines are emasculated by cylinder shutdown, turbochargers or overly efficient drivetrains.

No results found.