Noise and vibration characteristics: More comfort, more driver-fitness safety

Mar 26, 2013
As the flagship model in the Mercedes-Benz passenger car range, the S‑Class has a particularly high level of noise and vibration comfort. Relaxed travel and working is by no means just a luxury, but also helps to ensure driver- fitness safety - a driver who is mentally and physically fit has sufficient reserves to respond quickly and correctly in critical traffic situations, and will arrive at their destination less stressed.
The development goal of performance-enhancing comfort covers a wide interdisciplinary area. It begins with NVH measures (noise, vibration, harshness) relating to the body, suspension and powertrain, plus the dimensional concept for the interior, includes all aspects of suspension, climatic, seating and noise comfort and also incorporates the development of intelligent assistance systems.
The aim of the NVH measures for the bodyshell was to better the already very good preceding model with respect to vibration and noise comfort, but without dispensing with intelligent lightweight construction methods. The bodyshell structure of the new S-Class reaches new heights in dynamic rigidity thanks to new structural concepts and specific NVH measures in the bodyshell. These include:
  • Integral NVH front section concept consisting of extruded aluminium side members, cast aluminium elements at the transition between the front section and passenger cell, also at the damper domes, and integral supports as vibration-damping structural components
  • Increased use of bracing struts for specific increases in rigidity
  • Rear panel and cockpit cross-member of hybrid metal/plastic construction
  • Use of foam sections in the A/B/C-pillars to increase bodyshell rigidity
This created a very good basis for isolating engine and suspension-induced vibrations, and therefore for achieving the ambitious objectives with respect to vibration and noise comfort throughout the vehicle.
The aeroacoustic specialists took specific measures to counter wind noises during their aerodynamic development work. To reduce high-frequency wind noise, the sealing systems around the windows and door handles were above all improved considerably. The newly designed exterior mirror and the correspondingly shaped A-pillar with a minimised shoulder height ensure the efficient drainage of water and spray hitting the windscreen, prevent the airflow from breaking off at this point and therefore avoid noises that might enter the interior via the windscreen and side windows. The roof structure and the automatic tilting/sliding roof module were subjected to further aeroacoustic development to improve noise comfort in this area as well. In the case of the panoramic sliding sunroof, numerous air deflection measures, covers and seals with the appropriate geometry ensure the same high level of noise comfort as in the preceding model, despite the larger opening aperture.
A subdued, scarcely perceptible level of noise in the interior of the S-Class was the objective when configuring and coordinating the sound insulation measures. Particular attention was paid to transmitted engine noise and road roar. During the acoustic optimisation work, the focus was both on lowering the sound pressure level and on achieving the well-balanced and comfortable overall sound perception that is a hallmark of the S-Class.
To ensure that engine noise is perceived as refined and unobtrusive in the interior, the firewall insulation was extended into the side areas of the A‑pillars. Additional sealing levels were also added in the form of high-quality injection-moulded components.
A major contribution to the improvement in transmitted engine noise was made by improved insulation in the transmission tunnel area, as well as a modular engine partition made of plastic. The different noise characteristics of the engines are taken into account by the use of different weights per unit area.
The electrically adjustable rear seats available as an optional extra are free-standing. High-frequency tyre noise was reduced by a large area of insulation extending from the seat surface to the rear panel and parcel shelf. Breakthroughs are kept to a minimum. An intelligent air ducting system inside the parcel shelf allows the necessary ventilation while reducing noise transmission via the parcel shelf. The textile underbody and wheel arch cladding has an insulating and absorptive effect which reduces high-frequency tyre noise in the interior.