When my kids are in my car with me, they can sometimes hear an annoying high frequency sound. I assume that the frequency of the noise is too high for my "old" ears to hear it.

The length of the sound varies, and I believe that they can only hear it when the Distronic Plus Cruise Control is engaged.

Has anyone else run into this issue?

Thank you,

Christian

 

Yes , I can hear that as well !
Its indeed there using Distronic,
as well as putting the car in ' hold' when there is a someone in front of you.
I believe its the radar engaging ,but strange as the radar sits on the outside of the car ,so should not be hearable inside.. Btw mine is a 2006 W221 S500(EU)

 

The next time I am at the dealer, I will ask them if they are familiar with this issue.

 

The radar is on all the time (unless disabled completely from the cluster menu), it does not only come on when CC is active.

The 2006 car does not even have acoustic (ultrasound based) Parktronic (short distance) sensors like the facelift has. Someone might be able to hear the pulsing of these sensors.

Could be one of the many PWM operated actuators in the car.

 

Its interesting that I can only hear it ,using the Distronic when it needs to engage the brake; so guessing again its that actuator then..