The Sounds and Silence

It's really getting down to the detail work when the guys over in Engine Development get the call saying, "We've discovered that the Lincoln LS intender wants a throatier exhaust tone. Make it happen."

An oversimplification, maybe, but that's pretty much what's going on at Ford Motor Co. (and doubtless in other automakers' labs as well). Ford's even got a catchy buzzword for the work: "psychoacoustics," the study of how people perceive sounds.

What Ford's work amounts to is the testing of components - for today's discussion, we'll focus broadly on powertrain as a "component" - and the testing of individuals' preferences, with the goal of giving you what you want in, say, the intake note of a luxury car V-8 versus a pickup V-8. Ford's marketers and engineers get together to quantify what customers like - or hate - then employ a fascinating process to turn these "soft" preferences into hard engineering reality.

"If the marketing team says 'effortless power,' that's a cue for us," says Chuck Gray, Ford's advanced and pre-program powertrain NVH and CAE department manager. From there, a complex endeavor calling on several disciplines launches an effort to devise components to, in this example, make an engine sound like it has "effortless power."

Once the marketers have determined the need for such a sound, Mr. Grey says Powertrain engineers "play wargames with different hardware" in an attempt to deliver a comparable real-world engine tone.

"The skill comes in engineering the components to meet those targets," says Mr. Gray.

To measure the progress, engines sit in eerily muffled acoustic testing chambers with a precision gridwork of microphones strung above, gathering minute sound-signature information. Another single mic is placed in front of the engine to measure its gross sound level. Other mics measure "total airborne noise" to the driver, then a variety of different inputs - noise from the top of the engine, exhaust tone, intake sound - are studied to determine their individual contribution.

Equally complex, however, is the process of quantifying the sound "signatures" that become the testing targets.

In a room with some killer audio equipment and a United Nations-looking setup of long desks with sets of headphones, Ford hosts customers in what amount to psychoacoustics clinics. Here - or when Ford packs up the whole lot and takes it on the road - is where customers get paid to listen to sounds. They rate them for overall loudness and are asked for more esoteric definitions, depending on what Ford's trying to tease out of them.

Lording over it all is Norman Otto, senior staff technical specialist-body and chassis NVH department of advanced vehicle technology. Mr. Otto fell into Ford's relatively new study of psychoacoustics purely by chance: he's a chemical engineer who, by his own admission, was "looking for a career change."

Mr. Otto is charged with making sense of it all. He takes the sounds - and sometimes just the plain loudness, or lack thereof - and employs sophisticated sound-quality software to quantify the "target" noise.

The resulting squirrely graphs serve as the foundation data for an intricate "noise path tool," says Mr. Otto; the noise path tool becomes the "hard" data given to component engineers and testers in the hope that a new design or material change of an intake manifold, for instance, can deliver the desired result.

The testing is used for models already in production, says Mr. Otto, but because Ford's process is relatively new, a disproportionate number of new models is under pyschoacoustic testing.

"Sound quality (study) in general has been around Ford for eight or nine years," says Mr. Otto, "but only in the last year or so in relation to brand."

Ah, "brand." Therein lies the prime purpose of such involved testing. Ford believes psychoacoustics plays a big role in what differentiates brands for customers. That's why, as Mr. Gray says, specific customers are asked to evaluate specific sounds.

"After all, you'd like to not have an Escort owner specifying the sound quality for a Lincoln."

"If you're going to 'market' powertrain (as a brand identifier)," adds Mr. Otto, "you've got to understand what means 'sporty,' what means 'luxury.'"

Universities have bought into the idea of encouraging sound engineers, says Mr. Gray. Purdue and Penn State both have active programs, and he says most of the initial drive came from Europe, where one engineer authored more than 700 papers relating to the subject.

It appears that in the comparatively short time Mr. Otto, the converted chemical engineer, has tested people and components with the arcane science of psychoacoustics, he has developed a solid grasp of what's important about noise in a passenger vehicle.

"Powertrain noise is very emotionally tied to the identity of the vehicle," he insists. "The rest is just noise."

Nonetheless, Mr. Gray admits that sometimes psychoacoustics and the related testing still don't make the grade. Thankfully, "some of it still actually comes down to driving the car."