If the noise is from something under the hood, it should get louder with the hood open and quieter when the hood is closed. Otherwise, there is something in the power feed line, somewhere.
Plug wires are important, too, but if it's them, that noise decreases significantly when the hood is closed. Carbon-core type wires should only have a faint noise with the hood open and silent with the hood closed. Magnetic suppression wires generally have a slight bit more, but not much. Adding resistor spark plugs should be used with "wire" wire, but can be used anyway.
A whine might be related to the only part of the charging system that turns with the engine speed, the alternator. Might try grounding the case to the engine (using a valve cover or similar bolt). Then ground the engine to the body, ala GM, with a braided ground strap.
What about clicks from the brake light switch or similar, when they are operated? Might need to try grounding the case of the radio to the body, too, which an existing "back brace" would do.
Please advise of your progress.
CBODY67