Mystery A6/A4 speaker noises

[dmiller@iea.com (Doug Miller)]

Thought I'd see if any other A6/A4 owners on the list are having this
unusual occurrance.  My A6QW has the Bose system with factory CD changer.
I have been noting an intermittent electronic sound (faint buzzes) that
follows somewhat of a pattern coming over my audio system. It is unrelated
to the music being played, and to whether I am listening to AM, FM,
Cassette, or CD.  In fact, I recently discovered if I drive around long
enough with the volume all the way down, I can hear the sequence of buzzes
at the same volume, and the volume knob does not impact the volume of the
buzzes.

The sound itself is a high pitched buzz that occurs in groups of
approximately the same duration - a half second buzz and a second of
silence repeated 10 - 20 times and often terminating with a longer buzz.
It is at or near the threshold of hearing due to road noise underway,
though now that I've pointed it out to my wife, she recognizes it as well.
Its not very loud, mind you.  In fact, the first several times I heard it,
it was between songs on CDs and I thought it was the very faint clicks and
such that some discs have when they switch tracks.

Then I thought it was from my digital cellphone, a noise source discussed
here on the list as well as in my Audi literature.  It occurs without the
phone or power cord in the car however, so I ruled this source out.

Recently, I narrowed it down to the right front door speaker.  The stereo
itself and that speaker otherwise play normally, with good quality sound
for an OEM installation and no distortion.  If it were not for the fact
that the sound occurs with or without volume, I'd suspect a bad speaker,
but nothing else seems to be a problem with that speaker. The balance does
not diminish or shift the sound away from that speaker.  This says it is a
line level noise to my limited knowledge of electronics.

On a recent 30 hour straight through road trip alone in the car, I
experimented with every conceivable combination of fan speed, cruise
on/off, rear defrost on/off, lights on/off, etc and found nothing that
changed or impacted the sound in any way.  Nada.

If any of you have this same stereo in your car, or have heard something
like this before, I'd appreciate your input.  The last thing I want to do
is have some hamfisted mechanic ripping the stereo out of the currently
tight and rattle free dash to install another one under warranty.  Sorry
about the length, but I wanted to answer all the questions I thought I
would get in advance.


Doug Miller
dmiller@iea.com
97A6Q Wagon, 93 LandCruiser w/diff locks (and well used skidplates), 71
LeMans Sport V8 Convertible. Cannondale Super V 900 Comp.