About 30 miles north of Detroit—in Auburn Hills, MI—the global automotive supplier Faurecia operates a unique research and design
center. Within the 278,000-square-foot facility is a hemi-anechoic (half without echo) chamber where the supplier performs noise and vibration tests on seat frames and motor controls for new vehicles.
Both types of products are tested to ensure they meet automotive OEM standards or preference rating specifications. The products also need to meet Faurecia’s consumer tolerance thresholds.
A hemi-anechoic chamber’s walls, doors and ceiling are acoustically treated but not its hard floors. This kind of chamber is used to perform precision- and engineering-grade testing on products ranging from handheld devices to large vehicles and equipment.
Noise-control-technology specialist Eckel Industries Inc. of Cambridge, MA, designed and installed the Auburn Hills chamber over a nine-month period (June 2013 to February 2014). Testing began in April 2014.
The chamber measures 19 feet, 4 inches, by 28 feet, 10 inches, and is 12 feet, 2 inches high—making it the largest chamber in any of Faurecia’s 30 worldwide R&D centers. It features a 10-by-10-foot vehicle door and a 7-by-3-foot personnel door. An isolated floor prevents external vibrations from being transmitted into the chamber. It also features a silenced 2,000-cfm ventilation system.
The chamber has a cutoff of 100 hertz, which is the frequency at which the energy absorption drops below 99 percent or the pressure reflection exceeds 10 percent. All walls, doors and the ceiling are covered with
anechoic perforated metal wedges, each of which measures 34 inches long. To make the chamber immediately recognizable as Faurecia’s, Eckel painted some wedges blue.
Eckel’s team of designers and engineers worked closely with Faurecia’s building contractor. Christopher Kus, project engineer and noise, vibration and harshness specialist for Faurecia, says this cooperation kept the project on schedule, despite several layout revisions of the chamber.
Equally important, according to Robert A. Parmann, engineering director for Faurecia, is that the chamber exceeds the ISO 3745 standard for transmissibility. This standard requires a target base ambient sound level below 25 decibels, which is barely louder than a whisper. Eckel’s chamber is certified at 17 decibels.