Joe;

The whine you are hearing is not a result of any magic or "quiet deterioration" but simply the classic symptom of electrical noise found in all cars... gen. OR alt equipped!

Two sources exist, and both will be RPM dependent. Ignition (generated by high voltage, fast rise-time pulse in ignition wire, also sparks inside dist. cap.) and generator (more sparks at brushes), so in order to prevent it from being heard coming through the audio system, you must first determine which way it is getting into the audio system...either by way of the power line, or through the antenna, then take the appropriate steps to cure it (and they are different depending on which way it is getting in!).

If you hear it while listening to the radio only, it is likely coming in on the antenna. This requires ignition noise suppresion - "Suppression wires" are fine if you want to replace all the ignition wires, but so are o.e. solid copper wires...just add the 1k Ohm resistor spark plug ends which were o.e. on radio equipped later cars (Bosch PN ?).

If you just hear it when playing the radio, or a tape or CD, it's clear that the noise is coming in on the power line. This requires power line filtering. A capacitor (same as ignition type on distributor points line), located right at gen, wired from D+ terminal to gen housing is often very effective. Automotive Stereo places also have power line filters. Select a size approriate for the rated current of the car sound system, and wire it in according to their instructions...but try cap at gen first, also try relocating where you get the power for the sound system from....from wherever it is now, to directly from the battery terminal...if this helps, and you leave the power wiring there however, you must not forget to turn of the stereo manually every time (not relying on Ignition Switch) or you will drain battery.

The aforementioned preventatives are a starting point, and when used in combination will usually cure a whiney car audio system...sometimes however, eliminating electrical noise in vehicles can be quite tricky requiring a second tier of prevention. Repost if you need additional help.

Cheers