BMW is getting ready to pull the covers off its large electric sedan, called the i7. It’s set to be revealed later this year alongside the conventional new 7 Series range, as BMW isn’t doing two separate model lines like Mercedes is with EQS and S-Class.
BMW board chairman Oliver Zipse confirmed back in 2020 that the new flagship sedan would offer four powertrain options: petrol, diesel, plug-in hybrid and fully electric.
It seems BMW is particularly proud of the i7 version, and particularly its levels of noise suppression, given that the carmaker has released a whole wad of information on what it’s doing to eliminate unwanted sounds from its upcoming EV. Shutting up passengers will still be the driver’s responsibility, however BMW is adamant that it has virtually eliminated all other acoustic disturbances.
The acoustic test benches at the new branch of the BMW Group’s Research and Innovation Centre (FIZ) North 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.
Apart from 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.
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, in order to fully determine the acoustic properties of the new sedans.
This also includes precise alignment of acoustic pedestrian protection and the motor sound emitted in the interior of the vehicle. The i7 driver has a choice: characteristic silence or BMW IconicSounds Electric developed in collaboration with Hans Zimmer.
Furthermore, great importance was attached to noiseless power delivery of the electric motor. 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.
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 all aid this cause while also improving aerodynamics.
Further noise insulation measures
Effective and weight-optimised sound insulation is enabled by the use of innovative materials developed in conjunction with acoustic lightweight construction. These measures include sound absorbers incorporated in the pillar trim, seats, roof liner and rear shelf. These work together with the comfort glazing, which prevents unwelcome noise from entering through the window panes. There are also fleece elements in the doors and on the sill and wheel arch trim which reduce rolling noise.
Watch out for more information on the new BMW i7 and 7 Series models later in the year.
IOL Motoring