Noise-optimised tyres with foam absorbers are available for the Mercedes-Maybach on request. Foam material on the inside of the treads acts like a sound suppressor, making the interior even quieter. In addition, thermal and noise insulation laminated safety glass which also reflects infrared light is available all-round as optional equipment. The additional membranes between the layers of laminated safety glass also serve to reduce wind noise. They reduce noise reflected from guardrails or oncoming traffic as well.
Active road noise compensation is within the Daimler Group for the first time. The system reduces unwanted low-frequency noises using counter-phased sound waves (see separate section).
Mercedes-Benz engineers test vehicle acoustics in the technology centre for acoustics and vibrations (TAS) in Sindelfingen. This testing saw the first use of “Dascha”, a development dummy which self-generates the noises to be measured (Daimler noise source).
The TAS enables noises inside and outside the vehicle to be measured and analysed in different situations – here are some examples:
In one test laboratory, contact-free, fully automatic vibration measurements are carried out. The vibrations on surfaces are scanned with the help of lasers, then visualised as by a thermal imaging camera. The laser scanners are mounted on the arm of a robot moving along linear axes. (Simulated) excitation of individual vehicle components is carried out by a shaker. The system can measure both individual components and entire vehicles. To this end a crane is mounted on the laboratory ceiling.
The external noise roller dynamometers use microphone arrays, some of which have over 800 microphones connected in series. These enable passing noises to be simulated although the vehicle is stationary, whatever the time of year or weather. In addition the noise sources can be analysed. Sound-absorbing cones on the walls ensure the quietest possible room acoustics very similar to a free field.
High-frequency road impulses can be simulated at all four vehicle wheels on the acoustic and vibration comfort test rig. This takes the form of a flat surface test stand, and comes closer to reality than a roller dynamometer in terms of tyre-to-road contact. Different vertical and horizontal impulses are transferred to the wheels to simulate uneven road surfaces, including slab joints on motorways and rough asphalt.
The rain noise test station examines the noises generated by rainfall of different intensities on e.g. the roof and windows. Precisely 1648 water nozzles are installed in the high ceiling for this purpose.
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