The upcoming BMW i7 sedan is shaping up to be a truly special car. The Bavarian brand isn't messing about, putting the battery-powered luxury limousine through a series of challenging assessments, battling boiling temperatures in warm weather testing, and facing torturously icy climates near the arctic circle. This is, of course, to determine whether the electrified version of the 7 Series can cut it in an array of extreme situations.

Its latest test, however, focuses on a different (but still important) aspect of the luxury sedan; refinement and on-road mannerisms. In order to ensure occupants enjoy a peaceful and harmonious experience, the i7 has been subjected to BMW's extensive acoustic testing. This, says the brand, is done in order to determine which noises can be kept away from passengers, with numerous noise sources being taken into account.

Conducted at the Munich-based Research and Innovation Centre, engineers analyze the motor and rolling noise, as well as the aeroacoustics and vibration levels, to understand the acoustic properties of the electric luxury car. BMW notes this includes the acoustic pedestrian protection and the motor sound emitted in the interior of the i7. Called BMW IconicSounds Electric, the new development is a collaboration between the carmaker and famed composer, Hans Zimmer.

This clever piece of technology gives the driver a choice. They can either listen to the electric motor whirring away or enjoy the "emotionally powerful" sounds developed in conjunction with Zimmer. The near-silent power delivery of the electric motor is significant in reducing aural intrusion, but BMW has still gone to great lengths to reduce noise.

This includes acoustic optimization of the drive units and newly-developed noise encapsulation for the electric motors themselves. What's more, heightened front-end rigidity and tires with inner foam absorbers improve the acoustic and vibration comfort for the new i7 and upcoming 7 Series models.

But that's not the end of BMW's testing. Wind tunnel sessions allow engineers to examine the effectiveness of these refinement measures under extreme weather conditions. A climate test bench allows the carmaker to simulate an array of conditions and noise sources to better the acoustics of the vehicle.

This allows the brand to analyze and improve things such as the climate control and ventilation system. With aerodynamically designed body components and an almost completely closed underbody, the overall shape boasts not only low air resistance but aids in creating superb acoustics.

The brand's commitment to creating a hushed driving experience extends further than the vehicle itself. An acoustic simulator can play the noises heard in day-to-day driving, such as passing trucks and loud construction sites. Loudspeakers project these irritating sounds onto the prototypes in order to test the effectiveness of the vehicle's interior insulation.

BMW has used innovative, weight-optimized sound-deadening materials to create a peaceful environment. One way external noise is kept out is by the use of sound absorbers in the seats, roof liner, and rear shelf. Paired with comfort glazing windows, all the elements work together to keep unwanted noise out of the cabin. Despite the comprehensive testing, it doesn't stop there.

Lastly, BMW exposes the i7 to powerful electromagnetic fields in order to test the sensitivity of the electrical systems and how they react to interference. This, says the carmaker, ensures protection of the entire vehicle, allowing for reliable functioning of the suspension, safety systems, and several other items, such as navigation.

The all-electric flagship is shaping up to be a true halo car for BMW's electrified offerings and, judging by the harsh testing it has undergone, it will be a truly fierce rival to the Mercedes-Benz EQS. We simply cannot wait to see the plush duo duke it out.