Solingen, Germany - Automotive seating supplier Johnson Controls Inc. has strict requirements for acoustics in its seat systems, and its Sound & Vibration Lab at Solingen in Germany employs a team of acoustic engineers who specialise in this complex task.
As one of the most mechanically complex parts of an vehicle interior, the seat has numerous sources of noise, including gears, rails, springs and electric drives. This is where the work starts for Stefan Lingnau, head of this lab.
The goal is to eliminate unpleasant noises and ensure that the seat sounds good. Lingnau explains what "good" means in this context using the term 'value appropriate.'
"The individual noise profile of a seat must acoustically implement the customer's requirements and match the interior of the respective vehicle model."
As a result, the distinctive brand consciousness and different sound identities of the automakers play an important role. "The doors in a mid-level or luxury class model convey a brandspecific auditory experience when closed. With the sound design of seats, we are consistently continuing this experience into the interior, as well," said Lingnau.
In addition to the physical acoustics, psychoacoustic methods and knowledge are also essential for the engineers. With the aid of noise patterns, the subjective perception of sounds can be recorded, described and made measurable and reproducible. At the end of the development process, the seat has an optimally designed and coordinated sound profile.
The next step in sound management leads to the measuring technology utilised at the Sound & Vibration Lab. 'No people without machines and vice versa' is the rule of thumb there. All test benches and measuring instruments are developed in-house.
"We design test methods for the requirements, implement them onsite with hardware and software and calibrate the measuring instruments ourselves, as well," said Lingnau. Every new test bench is built in duplicate, and then the validation starts with a series of tests in a bi-directional procedure: One machine works with the values that the trained human ear of an acoustic engineer picks up and the other with data from the technical measurement alone.
"Only when the people and machines reliably reach the same result do we approve the new test bench. On average, that happens somewhere between the thousandth and three-thousandth test," said Lingnau.
Within a few years, the small series of acoustic measuring instruments in Solingen has grown to an internationally networked testing system that is globally unique. Using data lines, the acoustic engineers from the Sound & Vibration Lab always have their ear to the assembly line. Every seat from series production undergoes testing in all adjustment directions on the acoustic test benches. The sound data linked with the product series data is recorded. If a measurement exceeds defined tolerance values, the acoustic engineers are informed.
"We then get the sound clip via remote access, listen to it, look at the graphical information and start to analyse the fault. Often from thousands of miles away," said Lingnau.
Without even looking at the seat, the engineers can identify the root of practically every fault. They claim a 98 percent success rate in solving acoustic problems.