Milford, Mich. - Not unlike a finely crafted musical instrument, the 2006 Buick Lucerne - the nameplate's most premium model - was literally "tuned by ear" using advanced acoustic measurement and analytical technologies.
Throughout Lucerne's development process, GM engineers regularly used a sophisticated sound recording device nicknamed "Aachen HEAD" (pronounced AH-KIN) to capture sounds within Lucerne's interior while the car is in motion. An Aachen HEAD is a digital recording tool that closely matches the way humans process sound by preserving the binaural attributes of the sound inside or outside of a moving vehicle. The device, which mimics a human head of an average-sized person, incorporates specially calibrated, highly accurate digital microphones in each ear position. The microphones use a precise 24-bit recording resolution to enable dynamic range equal with human hearing.
"It's one thing to achieve numeric acoustical targets, but it's quite another to ensure that the sound being perceived by our customers is pleasing to the human ear, whether it's coming from the powertrain, body structure, or even the glove box as it is being closed," explained George Bei, Lucerne lead acoustical engineer. "By using the Aachen HEADs, we were able to subjectively identify and play back various sounds using digital filters at critical frequency ranges, which allowed us to craft an overall sound quality that harmonizes with the Lucerne's interior character we were striving for."
During live recording events, one Aachen HEAD - which is named after a University in Aachen, Germany - was placed in either Lucerne's front passenger and/or left rear passenger seat positions. Sound level testing was conducted at varying speeds over many road surfaces in dry and wet weather conditions. Hundreds of sound tests were conducted on the Buick Lucerne over the development cycle of the vehicle. "We paid attention to the fine details of sound quality in the Lucerne. We didn't just record powertrain, wind and road noise. We recorded and listened for sounds related to virtually every vehicle system, right down to specific components such as tires, HVAC, exhaust, door handles and more," explained Bei. "Our sound testing is a great complement to Buick's QuietTuning initiative."
After recordings were captured digitally, up to 20 engineers at a time assembled in GM's "Jury Room," an acoustically tuned facility that enables a uniform listening environment. The room is equipped with calibrated headphones worn by subjective evaluators that enable precise listening and rating of various sounds. To ensure uniform sound levels among all listening stations, the specially designed room is equipped with acoustic damping panels in the ceiling and walls.
The typical acoustic memory of the human ear to discern subtle yet important differences is about 10 seconds long - or about the time it takes to go from one vehicle to another. The Aachen HEAD and Jury Room are two tools of science that allow engineers to record and replay sounds under real-world driving conditions, fine-tune it and re-test until the sound quality levels desired are achieved. Sound quality comparisons and decisions that would normally take many days or weeks to complete using actual vehicles can be achieved in the Jury Room in the span of one to two hours. This significantly increases the development process.
"It's during the Jury listening process that we are able to evaluate multiple recordings back-to-back and make fast, accurate decisions," Bei explained. "This process allows us to strengthen the overall QuietTuning package for Lucerne. I believe Lucerne customers will be very pleased with the results."
QuietTuning is Buick's exclusive engineering approach to block, absorb and reduce the amount of road, wind, and tire noise from entering the interior cabin by using unique parts like laminated glass and steel. While the Lucerne exhibits leading levels of noise, vibration and harshness (NVH) characteristics - the vehicle's wind noise, road noise, and articulation index ratings are all among the best in the industry - its true auditory refinement is perhaps best measured in the subjective feel of how the vehicle sounds when it is in motion.
Through QuietTuning and interior sound level testing, the Lucerne is expected to be one of the most quiet, acoustically refined sedans in the industry - not just in terms of measured quantitative data, but qualitatively as well.
"Thanks to the Aachen HEAD and Jury Room, we were able to fine-tune Lucerne's acoustical cabin environment to a quietness level never achieved on a Buick offering - essentially setting a new standard of 'QuietTuning' in the process," explained Bei. "There are dozens of NVH applications on this car, and we validated or tuned every one of them through this process. It wasn't just about making the car quieter - that was a given. It was more about making sure we were audibly tuning the character of the car for our customers."
The all-new 2006 Lucerne will start to arrive in Buick dealer showrooms later this year.