Imagine your car's air suspension system as a balloon filled with air. When you unlock the door of your w211, the air suspension system gets ready to work. In the past, you might have heard a little 'hiss' sound as the air moved around, just like air escaping from a balloon. However, if you no longer hear this noise, it could be due to a few reasons.
One reason could be that the air suspension system has been designed to be quieter, so you don't hear the noise anymore. Car manufacturers constantly improve their designs to make things more efficient and silent, just like a ninja moving in the night without making any sound.
Another reason could be that the air suspension system might have been serviced or repaired, and during the process, the issue causing the noise could have been fixed. It's like when a magician fixes a broken toy and makes it work without a sound.
It's also possible that a component in the air suspension system might have worn out or failed, causing the system to not make any noise. This is similar to a musical instrument losing its ability to produce sound when a key part is broken.
Ultimately, not hearing the air suspension noise could be a good thing, as it might indicate that everything is working smoothly and silently, like a well-oiled machine that moves without a sound.