|July 7, 2002
Keep Listening Till There's Nothing to Hear! Audi's Creaking and Cracking Team Tracks Down Noises
If you do a job well, tell the world - loudly and clearly! This old business principle applies to Eckhard Peithmann in a rather different way. As head of the "creaking and cracking team" at AUDI AG, he and his "audience" track down all conceivable sources of noise - not just those in the team's ironic title - in the company's new vehicle families. During the development of a new Audi model, innumerable tests on the road and on test rigs are carried out until the last "creaking and cracking" problems are literally "driven out".
At Audi they call him simply "The Ear". Peithmann himself accepts this nickname with an amused smile: "This job not only calls for a sensitive ear but also a great deal of patience. Some noises can only be heard after the umpteenth test!" Others are not only heard but also felt. Peithmann selects his team members according to these criteria. The team consists of development engineers, and staff from the Quality Assurance, production and after-sales departments. "This work can't be taught at school or during a training course," says Peithmann. "In particular as a test of the individual's patience, it's not to everyone's taste."
But the task still appeals to him, even after more than 20 years. Peithmann (48) loves listening to the Blues; what he hates, on the other hand, are rattling glove compartments, squeaking seats or creaking plastic trim elements. The task is not merely to eliminate noises that really can't be ignored, but to get rid of those that only appear when certain road surface conditions, temperatures, speeds or distance are encountered or driven - and then begin to set the customer's teeth on edge.
Detecting all those sources of noise is a costly and time-consuming job. Noise analysis for any particular Audi model takes a whole year. Every four to six weeks members of the creaking and cracking team start out on another test drive - either in the bitter cold on test routes in Scandinavia or on desert tracks in North Africa. Depending on the complexity of the task, each of these outings may last between six and twelve days.
In between, noise is analysed on roller and shaker test rigs, in climatic chambers, with dummy-head microphones and on a hydropulse facility at Audi's technical development centre in Ingolstadt. "Over the years the number of test drives and noise analyses has increased; Audi has continuously expanded its model range and therefore new product launches occur at shorter intervals," Peithmann explains.
Why Audi's acoustic engineers choose for example the Arctic Circle to hunt for noises is explained by Carsten Vortanz, head of Design Check and Test Drive Procedures, and a member of the creaking and cracking steering committee: "During winter the temperatures there drop as low as minus 40 degrees Centigrade. At that level, plastics lose some of their elasticity, their friction coefficients alter and they are therefore more prone to produce noise." However, their properties also change when exposed to severe heat. Creaking and cracking noises in a car occur particularly often in plastics.
Moving parts in particular are liable to generate noise, for example seats, doors, seals or glove compartments. Squeaky leather too gives the testers the kind of earache they would sooner avoid. A fault evaluation key has been drawn up for all materials and components, with all noise defects recorded in the most objective possible way - but it's equally true that in the end, noise analysis will always remain a subjective evaluation.
Despite all the high-tech applications in use by Audi's acoustic analysis teams, the way the team members go about their work is not without a certain exotic aspect. One may see an acoustics expert lying in the boot "just keeping my ears open" - over bumpy tracks and surfaces suffering from severe frost and in widely varying road conditions. Alternatively, the tester on the front seat may suddenly lower his head into the footwell and listen for sounds inside the car - even if this means that his legs have to dangle precariously over the seat back. Vortanz: "We creep into every nook and cranny of the car's body." To avoid the risk of accidents, such test drives are not carried out on public roads but on closed test tracks.
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