Published on February 22nd, 2022 | by Subhash Nair0
BMW i7 Undergoing Acoustics Testing In Munich
The soon-to-be electric flagship from BMW, the BMW i7, is aimed at being the quietest car in its class.
The BMW i7, an electric version of the 7 Series that will debut later this year, has already undergone winter testing and is now going through another very important phase in its development – acoustic testing. Just like BMW Group’s Rolls-Royce electric vehicle, BMW’s aim with their electric luxury barge is to make it as quiet as possible.
BMW puts it this way:
“The level of well-being in the interior of the purely electrically powered luxury sedan is largely determined by the degree to which disturbing noises can be kept away from the occupants.”
The near-production prototypes of the i7 along with other 7 Series variants are all being tested at the Research and Innovation Centre in Munich (FIZ North). At this facility, engineers check the entire range of sounds that are produced by the i7 and that intrude into the i7 while it is being driven. This includes motor noises, rolling noises, aeroacoustics, vibration comfort. All of this while also ensuring the acoustic pedestrian protection sound emitter works to their satisfaction. This sound is part of the BMW IconicSounds Electric suite composed by Hans Zimmer. In fact, you can get the i7 to play these other IconicSounds Electric during motion or have it completely silent.
Here’s the press release with more information.
The driver of the BMW i7 has a choice: characteristic silence or BMW IconicSounds Electric developed in collaboration with 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 the requirements of electromobility 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. 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 that are relevant to day-to-day traffic anywhere in the world.
The BMW i7 aspires to redefine the high standards of the luxury segment – and this very much applies to acoustic comfort as well. Great importance was attached to noiseless power delivery of the electric motor. Contributing factors here 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 of the new luxury sedans to an outstanding level.
Acoustic testing on the climatic test bench and in the wind tunnel.
In order 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 and 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 – in particular 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 not only contribute to the low air resistance of the luxury sedan, they also help create its excellent acoustics.
Innovative materials for optimised sound insulation.
In addition to the noise and vibrations emanating from the vehicle itself, it is primarily the noise sources from the outside that can impair the experience of comfort while driving. 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.
Highly effective and also weight-optimised sound insulation is enabled by the use of innovative materials developed in conjunction with acoustic lightweight construction. One of the ways in which outstanding shielding of external 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 prevents unwelcome noise from entering through the window panes, this adds the final touch of perfection to the customer experience. There are also fleece elements in the doors and on the sill and wheel arch trim which reduce rolling noise, thereby maximising the experience of comfort.
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 so as to test the susceptibility of their electrical systems to interference and see how they interact with the environment.
The test engineers are able to analyse the diagnostic results transmitted from the vehicle in real time via fibre optic cables. The test programme in the EMC absorber hall enables comprehensive protection of the entire vehicle, ensuring absolutely reliable functioning of the suspension control and assistance systems and interference-free reception of online data, telephone, radio, TV and navigation signals.