/// AUTOMOTIVE ACOUSTICS TESTING \\\
Electromagnetic compatibility
With their detailed analyses and precise optimisation, the development and test engineers seek to ensure that the new BMW i7 offers what they believe to be the best environmental testing performance in the industry. This includes an analysis of electromagnetic compatibility (EMC). In the EMC absorber hall at the FIZ facility, prototypes of the car are exposed to powerful electromagnetic fields to test the susceptibility of their electrical systems to interference and see how they interact with the environment. EMC performance is an essential
criteria not only for comfort and usability of the product, but also for certification against international standards for the markets into which the vehicle will be sold. To achieve this, test engineers are able to analyse the diagnostic results transmitted from the vehicle in real time via fibre optic cables and build a comprehensive picture of the radio frequency environment of the car so it can be mapped against different criteria – both the company’s own requirements and
well as other aspects of quality. Therefore, a lot of importance was attached to noiseless power delivery of the electric motor. Con- tributing factors here include acoustic opti- misation of the electric drive units, a model-specific mount concept and a newly developed noise encapsulation for the elec- tric motors. Taken together, these measures enable the BMW i7 to achieve effective acous- tic decoupling across a wide frequency range, thereby ensuring maximum acoustic comfort in the interior in all driving situations. As a re- sult, the driver of the purely electrically pow- ered car always has the choice of enjoying either the characteristic silence of the motor or the emotionally powerful BMW Iconic- Sounds Electric sound system. Increased body rigidity at the front end and
tyres with a foam absorber on the inside for integrated noise insulation likewise help raise the acoustic and vibration comfort.
Climatic and wind tunnel testing \\\ In order to be able to test the effectiveness
of all measures under extreme climatic con- 14 /// Climate & Vibration Testing \\\ 2022
The very large EMC test hall in Munich has the capacity for full vehicle electro-magnetic compatibility testing
those of the standards bodies. The test programme in the EMC absorber hall enables comprehensive protection of the entire vehicle, ensuring absolutely reliable
ditions too, the development engineers at FIZ North use an acoustic climatic test chamber specifically designed for this purpose. There, all globally relevant conditions can be simu- lated and a wide variety of noise sources can be analysed and optimised, such as the acoustics of the air conditioning and ventila- tion system throughout the entire vehicle – in particular at very low or very high tempera- tures.
In the same way as the motor and tyre
rolling acoustics, ambient noise can also be selectively reduced. For this purpose, the aero-acoustics of the BMW i7 are perfected in the acoustic wind tunnel. Clear-cut body sur- faces, flush-integrated door handles, aerody- namically optimised exterior mirrors and an almost completely closed underbody not only contribute to the low air resistance of the car but also help create its excellent acoustics.
External noise simulation \\\ In addition to the noise and vibrations ema-
nating from the vehicle itself, it is also the noise sources from the outside that can im-
functioning of the suspension control and assistance systems and interference-free reception of online data, telephone, radio, TV and navigation signals.
pair the experience of comfort while driving. The new acoustic simulator at FIZ North en- ables the noise emitted in day-to-day traffic to be simulated under laboratory conditions – this includes the sounds made at road con- struction sites and by passing trucks, for ex- ample. Numerous loudspeakers are used to project these sounds onto the vehicle proto- types from all directions to test the effective- ness of the interior noise insulation. Highly effective and also weight-optimised sound insulation is enabled by the use of in- novative materials developed in conjunction with acoustic lightweight construction. One of the ways in which outstanding shielding of ex- ternal and intrinsic noise is achieved is by means of sound absorbers incorporated in the pillar trim, seats, roof liner and rear shelf. Together with the comfort glazing, which pre- vents unwelcome noise from entering through the window panels, this adds to the overall acoustic performance of the vehicle. There are also fleece elements in the doors and on the sill and wheel arch trim which re- duce rolling noise. C&VT
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