With the introduction of MBUX – Mercedes-Benz User Experience, a completely new challenge was the acoustic feedback when operating the functions using the touch controls in the steering wheel. This not only meant generating a pleasant and natural operating sound, as the speed of the acoustic feedback is also very important: it must take place with no discernible delay, so that the subconscious perceives the connection between operation and feedback as natural.
This time constraint was not a trivial matter, as the touch controls actuate very different control units. This also made generation of the sound a challenge, as it had to sound the same for all functions even if coming from different loudspeakers. The reward for these efforts, which also involved a large number of customer tests, is the special sound when scrolling down to the end of a menu.
Similar efforts went into the sound of the indicators, citing the natural rhythm of conventional relays. The volume is graduated to suit the ambient noise, so the acoustic feedback is never obtrusive but always easily audible.
Adaptation to the ambient noise level is also a principle behind the bouquet of warning sounds that were newly defined, composed and integrated for the new GLE. Empirical customer tests were conducted to ensure that the sounds are prominent but not irritating, and that their urgency suits the situation. The acoustic warnings are graduated according to priority: the warning that a passenger is not wearing a seat belt is less urgent than the alarm when there is imminent danger of a collision. Though this is by no means has the intensity of a siren: the aim is to claim the driver's attention without paralysing him/her with a shock effect.