Whistling noise from speakers

["hotrod930" <hotrod930@xxxxxxxxxxxxx>]

the whistling noise that changes with rpms as you drive, and is noticeable
mostly when music is low or not playing is referred to alternator whine.

I'm willing to bet you that there is a cheap, low quality amplifier
somewhere in your car, and/or a poor quality installation.

Noise filters and the like don't do anything more than occasionally reduce
the noise slightly.  Sometimes they make it worse!  A quality installation
with quality components should yield very little or no noise at all.  That,
and properly adjusted system settings.

Once you find the amplifier, you can try turning down the sensitivity/gain
adjustments on it, and that may reduce or eliminate the noise while
hopefully still leaving plenty of "volume" in your system.  If your stereo
volume control has a scale of 0-40, or 0-35, it's fine to have your system
reach it's actual peak, undistorted output close to the end of this scale.
I'm not sure if this makes sense.  Some people like to have their system
reach 80% of it's output when they've only turned the volume up slightly,
but this only makes it "appear" to be a louder system.  The system will
still reach it's limit and start to produce distortion at some point, who
cares if it's at "15" instead of "40" on a scale of 0-50 on the head unit.
(You know when you've got a nice loud system when it actually drives you out
of the car before you hear any audible distortion.)  Back those gains down
and see if you can reduce the noise to a tolerable level and still have
enough volume left in the knob to reach either your's or the system's
limits.

I don't know if I've been any help at all, but questions emailed directly
are welcomed nonetheless....

- -Rod