Please send questions to Car Audio and Electronics via e-mail: techpanel@mcmullenargus.com
I have an engine noise-type question for you. First of all, let me tell you what my audio system consists of: Eclipse 55040 CD player; two PPI amps: the 650 runs sub and fronts (six-channel amp running three channels), 250 runs the rear fill; MB Quart QM215.61 separates in the front, RKC-110 coaxials in the rear (not sure exactly on the coaxial model), and JL 12WD4 for low-end frequency - all in a 1999 Isuzu Rodeo.
I seem to have a hiss in my system that I can't get rid of. When I put the CD player on pause, I can hear the noise from my higher frequency speakers. This noise is below any recording noise that may be on any given CD. Any other system in the car (lights, AC, etc.) does not affect the loudness of the noise. Obviously, I can't hear it when the music is playing, but some cable or component in my car is picking up noise. I am guessing it can't be any of the amps because I am getting noise from all of my higher frequencies. I believe I think I have it narrowed down to the CD player and interconnects from there that run the full length of my car.
By the way, I have had a local shop tell me there is nothing I can do and I refuse to believe them.
I would appreciate any advice you can give me about this noise.Thanks,Chris ParrWisconsin
Good thing you didn't settle for putting up with the noise. Most noise problems are predictable, in that trained installers know how they have had to fix past examples, and prevent them by not repeating techniques that lead to noise. The rest are generally solvable, if the installer approaches the problem as a challenge that requires a bit of thought.
Logical troubleshooting techniques are the key. By understanding what causes noise, quick tests can be performed that eliminate false leads. The first test is to determine which of the four main types of noise is present. Power line noise travels up power lines and other physical wires and into components, where it is played as if it were music. Radiated noise travels through the air, from a source that releases electromagnetic radiation (EMR), which is picked up by a piece of audio equipment. Ground loop noise occurs when more than one component is grounded to more than one location in the vehicle. A similar problem called "Loop Area Noise" can infect cabling that travels through the vehicle.
All noise that is caused by the vehicle and its systems falls into one of those three categories. What you hear can also come in a variety of types that identify the source producer of the noise. A high-pitched whine that varies with engine speed begins at the alternator, and may increase in intensity when your headlights or rear defogger are turned on. Pitch of the whine varies clearly in relation to the amount you press on the gas pedal while the engine is running.
A buzzing that also varies with the engine speed is called "ignition noise" since it is sourced from the spark plug wires, plugs, and other very high-voltage components. A constant buzzing that does not really vary directly with the engine RPM can be produced by modules like daytime running light units or pulse-type dimmers. A complex tone that varies a bit and sounds like much more than a simple alternator whistle would likely originate from a microprocessor or computer.