Ammi

I've recently noticed that when I'm just cruising, the volume of my radio/cd fluctuates by itself, meaning sound increases and decreases enough that I have to manually adjust the volume. Anyone know what the problem might be?

Peter_02AMG

That's normal, the volume increased as the engine noise increased. My E55 &997 turbo is the same way.

Ammi

It's normal? I don't think you understood my problem. Sound shouldn't fluctuate when I'm just cruising at a certain speed

amdeutsch

It depends a lot on the surface you're driving on. What kind of noise it creates. Is it uniform. Etc.

Peter_02AMG

Yes it is normal, It's one of the function of the Audio 50 system you have in your car. There a microphone located by the ignition switch that pick up extra noise level from the vehicle speed, engine noise, road noise or noises inside the vehicle so your radio automatic increase or decrease the volume to maintain the set sound level.

Page 21, second paragraph "Automatic volume control" of your Audio 50 owner manual.