There are ways to reduce or eliminate the buzzing and high-frequency noise that the engine adds to your in-car audio.
Despite the fact that we spend so much of our time listening to music in our cars, the automobile is a fairly hostile environment for someone seeking audio perfection. The alternator of the car and the electrical pulses from the spark plugs both create oscillating electronic currents in the audio signal. Really, any moving electrical part can create magnetic waves that show up in electrical wires as audible noise. This is why cables are shielded.
The power from the 12V car battery that powers your car computer fluctuates from 12–14V and includes many other little electrical oscillations from the car. While the battery can still successfully power your computer, the little fluctuations pass through the computer and show up in the analog audio signal that it puts out. At other times, the car's electrical noise is picked up directly by audio wires that act as a sort of antenna. This line noise can mess up the audio on its way from the computer to the head unit or the speakers.
Just as there are many potential causes for line noise, there are a number of ways to reduce the noise in a car computer setup. We'll look at those now.
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