The new BMW i7 is undergoing a diverse range of tests in the BMW Group's laboratories and on its test benches. The testing programme is also designed to ensure electromagnetic compatibility. The BMW i7 is being developed to combine hallmark driving pleasure with an exceptional comfort level. There are various potential noise sources to be considered, so near-production prototypes of the BMW i7 – and indeed all other model variants of the future BMW 7 Series – undergo an extensive programme as part of their acoustic Testing.
At the Research and Innovation Centre (FIZ) in Munich, test and development engineers check the full range of the vehicle's sound emissions and immissions. Motor and rolling noise are analysed in detail, as are the aeroacoustics and vibration comfort, to determine the new luxury sedans' acoustic properties fully. This also includes precise alignment of acoustic pedestrian protection and the motor sound emitted in the interior of the BMW i7 – the latter having been developed as part of BMW IconicSounds Electric, a collaborative venture between the BMW Group and Hollywood film music composer Hans Zimmer.
The acoustic test benches at the new branch of the BMW Group's Research and Innovation Centre FIZ North are specially designed to meet electromobility requirements and enable all driving situations to be simulated realistically. Here, any irritating noises registered by development engineers during test drives on the road can be recreated and selectively eliminated. Furthermore, roller dynamometers with a unique quiescent level and interchangeable surface coverings enable the measurement and validation of drive acoustics and tyre noise on all road surfaces relevant to day-to-day traffic anywhere in the world.
Contributing factors include acoustic optimisation of the electric drive units, a model-specific mount concept and a newly developed noise encapsulation for the electric motors. Taken together, these measures enable the BMW i7 to achieve effective acoustic decoupling across a wide frequency range, thereby ensuring maximum acoustic comfort in the interior in all driving situations. As a result, the driver of the purely electrically powered luxury sedan always has the choice of enjoying either the characteristic silence of the motor or the emotionally powerful BMW IconicSounds Electric developed in collaboration with Hans Zimmer.
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 to an outstanding level.
Acoustic Testing on the climatic test bench and in the wind tunnel.
To be able to test the effectiveness of all measures under extreme climatic conditions too, the development engineers at FIZ North use an acoustic climate test bench specially designed for this purpose. Here, all globally relevant conditions can be simulated. A wide variety of noise sources can be analysed and optimised, such as the acoustics of the air conditioning and ventilation system throughout the entire vehicle – particularly at very low or very high temperatures.
In the same way as the motor and tyre rolling acoustics, ambient noise can also be selectively reduced. For this purpose, the aeroacoustics of the BMW i7 are perfected in the acoustic wind tunnel. Clear-cut body surfaces, flush-integrated door handles, aerodynamically optimised exterior mirrors, and an almost completely closed underbody contribute to the luxury sedan's low air resistance and help create its excellent acoustics.
The new acoustic simulator at FIZ North enables the noise emitted in day-to-day traffic to be simulated under laboratory conditions – this includes the sounds made at road construction sites and by passing trucks, for example. Numerous loudspeakers are used to project these sounds onto the vehicle prototypes from all directions to test the effectiveness of the interior noise insulation.
Intense Testing of electromagnetic compatibility.
With their detailed analyses and precise optimisation, the development and test engineers seek to ensure that the new luxury sedans offer the best comfort experience ever realised in a BMW. This also includes an analysis of electromagnetic compatibility (EMC). In the so-called EMC absorber hall at the FIZ, prototypes of the new luxury sedans are exposed to powerful electromagnetic fields to test their electrical systems' susceptibility to interference and see how they interact with the environment.
The test engineers can analyse the diagnostic results transmitted from the vehicle in real-time via fibre optic cables. In addition, the test programme in the EMC absorber hall enables comprehensive protection of the entire car, ensuring reliable functioning of the suspension control and assistance systems and interference-free reception of online data, telephone, radio, TV and navigation signals.
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