The Quest for a Quieter Ride

The Wall Street Journal

Stepped-up efforts to nix the chirps, rattles and drones

By JEFF BENNETT 

Updated Jan. 8, 2014 8:28 a.m. ET

After making huge strides in damping engine, road and wind noise, car makers are facing a new problem: Drivers are hearing—and being bugged by—a lot more interior sounds. Jeff Bennett takes a look at how car makers are creating more hushed interiors. Photo: General Motors.

It's a paradox of today's advanced car design: The more auto makers succeed in muting sounds coming from outside, the more drivers are hearing the annoying little chirps, rattles and drones on the inside.

Now, after making huge strides in diminishing the worst offenders—engine and road noise—auto makers are going to new lengths to quiet their vehicles' interiors, fine-tuning acoustics on everything from the whoosh of the climate-control vents to the ka-thump of the door locks.

Some auto makers are taking cues from airplane cockpit design, adding sophisticated noise-cancellation systems to offset certain sounds. And parts makers are conducting extensive frequency testing at the behest of car companies, only to add a little extra padding here, mix some plastic into the metal there or just remove an offending part.

Leigh Wells

Car Cacophony

Some ways the auto industry is trying to damp unwanted interior sounds

Growl, Gurgle

SOURCE: Gas engines

FIX: In some hybrid electrics,a noise-canceling system uses in-cabin microphones to detect engine-noise frequencies, then emits opposing frequencies through the car's sound system.

Whine, Whirr

SOURCE:C ooling and heating system

FIX: Some companies are eliminating whiny brushes in the air conditioning units; others are rearranging the blower blades.

Ka-Thump, Ting

SOURCE: Door-locking system

FIX: To eliminate an annoying metal-on-metal sound, one company is mixing plastic into the latch mechanism.

Whoosh, Whistle

SOURCE: Door frames, windows

FIX: Some companies are adding transparent plastic into the windows. Another changed its door design so the top edges fit into the side of the vehicle instead of wrapping over the top.

Rumble

SOURCE: Road noise at your feet

FIX: Auto makers are trying a variety of new approaches, from testing different-width tire treads to adding more sound-deadening materials in the wheel well.

Various Outside Sounds

SOURCE: The neighbor's snowblower, construction jackhammers

FIX: Thicker, sealed windows, enhanced inner-door insulation.

"Ten years ago most interior noises couldn't even be heard because of the engine and road noise," says John Tepas, vice president of engineering at Mahle Behr Troy Inc., the Michigan-based subsidiary of Mahle GmbH, an auto-parts maker that produces such components as heating, air-conditioning and ventilation systems. Recent progress in damping those sounds, he says, has forced manufacturers to lower noise levels "even on little parts like the tiny motor that runs the vent door that opens and closes in a heater."

At the sound-testing lab of lockmaker Kiekert AG, in Wixom, Mich., engineers try to optimize latch sounds.David Lewinski for The Wall Street Journal

A hushed ride used to be a bragging point exclusive to the luxury-car world, a sign of a car's refinement. But in recent years, the quest for quiet has trickled into more high-volume vehicles—and even the brawny world of pickup trucks.

In introducing its redesigned 2014 Silverado pickup truck recently, General Motors Co.GM -0.25% devoted a 30-second commercial to its quiet cabin, which the manufacturer credits to upgrades like enhanced baffling inside the doors and thicker, better-sealed windows. To cut down wind noise, engineers inlaid the cab doors so that their top edges no longer curve over the rooftop, a design that had unintentionally created a kind of wind tunnel.

Car noise is becoming a big problem for car makers. That's because, dealers say, more owners are bringing in their new vehicles for repairs after hearing noises—even when nothing is operationally wrong. The trips drive up warranty costs for auto makers and hurt the perception of a car's quality, industry analysts say.

"It's frustrating for the customer of a new car to come back and report a sound, only to be told by the dealership that it's normal and there is nothing they can do about it," says Mr. Tepas.

To quell the frustration, quiet labs have been popping up around the car industry.

The electric Cadillac ELR uses new noise-cancellation technology General Motors

Chevrolet now boasts a quiet cab in its Silverado pickup. General Motors

Mahle Behr spent more than $1 million to develop its Troy, Mich., sound-testing facility, which includes two acoustic rooms built on shock absorbers to stop noise from bleeding in through the ground.

In one room, the skeleton of a car cockpit is connected to a massive air chamber, while a tripod-mounted microphone records and measures every whoosh. Niranjan Humbad, Behr's acoustic validation manager and a 25-year noise-tracking veteran, listens to the sounds and reviews visual representations of them on the computer to target problems.

Mr. Humbad and his team have compiled a database of more than 1,000 noises caused by the motor and blowers inside a car's heating, ventilation and air conditioning (HVAC) unit, ranging from low throaty rumbles to a high-screeching whistle or chirp tone. The database is used with computer software to help identify which sounds need muffling.

The Hush-Hush List

Here are some of the most muted cars on the road, according to Consumer Reports' most recent tests.

Audi A6

BMW 535i

Cadillac XTS

Chevrolet Silverado 1500

Chrysler 200

Hyundai Genesis

Lexus ES 350

Lincoln MKZ

Mercedes-Benz ML350

Ram 1500 Big Horn

Tesla Model S

(Source: Consumer Union)

To develop a silent blower for the HVAC system, for example, Behr engineers have begun geometrically rearranging the blower's blades.

"Imagine a hamster wheel lying on its side spinning around in the middle of a fat soup can," Mr. Tepas said. "We cut the sound by changing the distance of the blades on which the hamster's feet run."

Noises and sounds are always going to exist, Mr. Humbad says. "The trick is turning down those noise levels that the human ear doesn't like."

Or finding a way to mask them. The 2013 Ford Fusion Hybrid and the new-to-market 2014 Cadillac ELR electric-hybrid vehicle are among several cars now boasting "active noise-cancellation" technology that electronically draws information from ceiling-mounted microphones in the cabin to detect—and zap—unwanted exterior and interior sound. The ELR runs on electric power and then switches to a gasoline engine when the charge runs out.

"So the engine is absolutely quiet when the ELR is running on electric and we didn't want to break that spell when the gasoline engine kicks in," says Doug Koons, lead noise and vibration engineer for the ELR. Once microphones pick up the sounds of the gas engine, a microprocessor sends out a bandwidth of low frequency through the car's audio system to cancel out that noise.

Mr. Koons says active noise cancellation is a new frontier for the auto industry. In the future, say engineers, auto makers may even allow customers to flick on a "white noise" option.

To most consumers, the "thump" of a closing door or lock conveys the quality of the vehicle—the quieter, the better. "Sound, or in some cases the lack thereof, builds on a consumer's perception of quality," says Gene Petersen, a senior engineer and noise tester for Consumers Union, which publishes Consumer Reports.

Lockmaker Kiekert AG, which provides latch systems to brands like Mercedes-Benz DAI.XE +0.10% and Bentley, has built an acoustic lab at its 90-person production facility in Wixom, Mich. Kiekert has recorded thousands of different door-locking sounds from its own products and those of its competitors.

"A high-frequency sound you get from metal hitting metal is usually perceived as bad because the tingy sound is annoying to the human ear," says Mike Hietbrink, vice general manager of the company's U.S. operations. "A lower sound like a closing bank vault is considered more acceptable."

To minimize the ting, Kiekert is experimenting with incorporating different materials into a lock's construction. For example, mixing in or overlaying plastic onto the metal lock latch that connects to the door's metal post creates a bumper against sound.

"Think of the lock and catch coming together like banging a tuning fork on a table," Mr. Hietbrink says. "That's what we are trying to change."

Write to Jeff Bennett at jeff.bennett@wsj.com