The Sound of Silence

TMNA R&D engineers engage in ‘constant battle’ to eliminate unwanted noise and vibration in Toyota’s vehicles

February 28, 2017

The Evaluation Guys -- Gordon Ebbitt (left) and Todd Remtema spend quality time in this anechoic chamber at TMNA R&D, measuring the noise levels inside Toyota and Lexus vehicles currently in development. (Photos by Brian Watkins)

Odds are, you’ve never heard of Todd Remtema and Gordon Ebbitt. And they’d kind of like to keep it that way.
 
That’s because both work behind closed doors in Vehicle Development at Toyota Motor North America Research & Development (TMNA R&D) in Ann Arbor, Mich., focusing specifically on noise and vibration. So if they and their colleagues have done their jobs, the next time you’re driving down the road in the Toyota vehicle of your choice, you won’t notice anything.
 
Unless they want you to.
 
“Actually, with this vehicle, we’re trying to add sound to the interior,” says Remtema, pointing to a future product resting on rollers in an acoustic anechoic chamber—a special room that’s designed to absorb echoes. “It’s going to be the high-grade sports version of this particular car, so we’re enhancing engine and exhaust notes with added sound through the speakers so it sounds more sporty.”
 
Most of the time, this duo strives to do just the opposite: identify and eliminate noise and vibration generated by the engine and exhaust that tries to seep into the passenger cabin. Remtema, who manages the group, and Ebbitt, a senior principal engineer, have ways of putting a stop to all of that. But first they need to know exactly what they’re dealing with.
 
That’s where their purpose-built test facility comes in.
 
“These types of rooms were first developed around the time of World War II,” says Ebbitt amid the eerie quietness. “The goal is to create an outdoor environment indoors. If we tried to test this vehicle in a parking lot, the sound would just move away from us and keep on going. Here, it gets absorbed.”
 
Tricks of the Trade
 
In addition to the test chamber, the team uses specialized components to help isolate specific sources of discord. One example is a BAM. That’s short for a big auxiliary muffler. It can take the vehicle’s exhaust out of the equation so the testers can focus on what’s emanating from the engine compartment.
 
Microphones and accelerometers, placed strategically inside the car, are another trick of the trade. Rather than rely on their ears that are susceptible to subjective judgments, Remtema and Ebbitt collect objective noise and vibration data. This data is then analyzed to determine the important noise paths and set appropriate system level or component level targets. The “evaluation guys,” as they refer to themselves, then share these numbers with the “modeling guys” who use computer-aided engineering software to design the actual vehicle components. In all, dozens of engineers and technicians focus exclusively on noise and vibration.
 
“We primarily develop for engine noise, engine sound, road noise, and cruising quietness.  However, we also develop for noises such as gear noise and cooling fan noise,” says Remtema.
 
“And we do a lot of benchmarking,” adds Ebbitt. “We need to know where our vehicles are compared to our competitors.”
 
 

“Shoddy” Work

As the tools to measure noise have become more sophisticated, so has the technology to either eliminate or mask it. Take, for example, carpet. In the past, Toyota attached die-cut pieces of padding to the underside of the carpet to serve as a buffer between the body panels and the interior. Though helpful, it was an imperfect solution – with gaps between the pieces serving as pathways for noise.
 
Today most new Toyotas benefit from a seamless layer of molded injection fiber that helps to cover up to 90 percent of the area where exterior noise tries to get through the floor panels. The die-cut approach tops out at 60 percent.

Like so much of what Remtema and Ebbitt do, that layer of “shoddy” – as they refer to it – is there, but you’d never know it.
 
“A huge amount of technology goes into that,” says Ebbitt. “It’s nothing you can see. But you can hear it. Or not hear it. It’s like the insulator in the dash and the sound absorber inside the hood. No one sees them. But we think about them a lot. We’re always looking for ways to make the passenger compartment quieter. It’s a constant battle.”
 
And, often, it’s a balancing act. Remtema and Ebbitt could easily eliminate all unwanted passenger compartment noise. But many of their remedies would add weight to the vehicle at a time when designers are trying to trim pounds to help boost fuel efficiency.
 
Getting it Right
 
Still, Remtema and Ebbitt continue in their never-ending search for incremental improvement – tapping into their combined 54 years of experience in this specialized field, along with advanced degrees in mechanical engineering and acoustics. When TMNA R&D gets it right, customers appreciate it. Even if they don’t know why.
 
Take, for instance, the current Avalon.
 
“What’s success look like for us?” says Remtema. “I’d point to the Avalon. That’s a very quiet car. And a lot of what we learned developing the Avalon went into the current Camry, which was a big improvement over the previous generation.
 
“Besides,” he continues, “my in-laws bought an Avalon. They are very happy with how quiet it is. I’d definitely classify that as success!”
 
By Dan Miller

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