pokerFACE

I can't recall if we have speed-sensitive volume / active-noise cancellation (not likely) on our audio system for the W203 (mine is a 2001 C240 specifically, stock, non-Bose), and/or if we have a microphone pre-wired inside our car.

Just this week I started noticing a feedback, the type you'd get if you stick a microphone in front of a speaker at speed. It only occurs within the speed range of 120 - 125kmh, and only if I'm accelerating. Consiering that 120 is my usual cruising speed, it's pretty darn annoying unless I turn up my radio way way up.

Note that I've tried various combinations (radio off / hvac on, radio on / hvac off, all off, all on), and the problem still surfaces.

any ideas?

jedcred

Is it an increasing feedback noise or just a constant whine? I had a constant whine problem when I installed my new speakers; turns out the speaker wires in the wire conduits were too close to the power lines that run along the bottom of the conduit. It could be that after kilometers of driving they slipped down the conduit and are near the power lines, causing this kind of feedback.

As a quick test, try listening for the sound with the radio on (but turned all the way down) with the key in position 1, then position 2 (which gives power to the rest of the car). The sound could be there, but just barely, and you only noticed it when it got loud enough when you were accelerating. If so, this is probably what has happened.

pokerFACE

I'll try doing that the next time I get into the car.

However, it is an increasing noise, from 120 topping out at 125, then it disappears. I've driven in and around the city at lower speeds and I do not hear anything else.

I don't get it though.. I thought we had fibre-optic cabling in our cars? And I can't exactly place the source of the feedback (if it came from a particular speaker).

Benzonline

The cd changer to head unit is fibre optic connection only.

It could be your head unit.