How to choose a noise suppressor

Dealing with system noise


Crutchfield Writing Team

The Crutchfield writing team is a group of full-time, in-house copywriters who share a passion for consumer electronics. In addition to creating the articles and videos you find in the Research area of the Crutchfield website, these hard-working and talented people write the informational copy for the products on our website and in the Crutchfield catalog. Our writers constantly research the latest products, technologies, and industry trends, so that we can bring you the most helpful information possible.

More from Crutchfield Writing Team

  • The type of noise suppressor you need depends on what is causing the noise in your system. Obviously, the trick is to determine what the source of the noise is. The information below may be helpful in finding the culprit.
  • Read over this article for some hints and explanations of what can cause noise in your system. Then use this diagnostic flowchart as a guide to walk you through the troubleshooting process.
  • Most products purchased from Crutchfield qualify for our expert tech support. If you purchased your gear from Crutchfield, or purchased tech support separately, don't hesitate to call on our tech support staff (have your Crutchfield invoice handy).

Dealing with noise

Noise can be introduced into your system from a number of sources. This is especially true if you have an amplifier. The type of noise you're hearing can help determine the cause.

If you have an external amplifier in your system, the first thing to do is to quiet any system noise, which sounds like a constant, low hiss. First, check for system noise with the engine off. Insert a blank tape or put your CD player on pause. Listen to the system with the volume completely down, then completely up. Put on music. If you hear hiss in either instance, adjust the gain on your amplifier.

Pass more signal from the receiver to the amp by leaving the receiver's volume higher before you set the amp's gain. Experiment until you eliminate the hiss or reduce it as much as possible. A tiny bit of hiss is OK — you won't hear it while driving.

Engine noise

If your problem is related to engine noise, you may hear a whining or clicking sound. Its pitch will vary with engine speed. Most noise problems come from a poor ground. Always make sure your ground wire is connected firmly to bare metal in the event of a noise problem.

You can also try isolating your amp from the chassis of your vehicle by mounting it on a board or using rubber grommets or feet; using a different brand of patch cables; or, only if all else fails, installing a noise suppressor. The tricky part is figuring out which step or steps to take. Please read the rest of this section and try some of the simple tests.

Noise in the patch cables

Noise can be picked up by the RCA patch cables connecting your components. To test this, detach the cables from your amp. Insert one side (left or right) of a spare patch cable into the amp's left and right input jacks (see illustration below). Turn on your system and engine.


If the noise is gone, reconnect the cables to the amp, and disconnect them from your receiver. If you hear the noise, your patch cables are definitely picking it up. Try re-routing them. Separate them from your power cable by at least 18 inches. You could try a better brand of patch cables. The inexpensive RCA cables many people use to connect their components don't have the insulation or conductivity necessary to deflect noise in a metallic, highly conductive automobile.

How much noise your cable receives depends largely on the size of its loop area; the larger the loop area, the more vulnerable your cable is to induced interference. A cable's loop area is equal to the distance between its center conductor and outer shield times the length of one complete twist in a twisted pair configuration, or the entire length of the cable in a coaxial type. Consider trading your old cable for one with a twisted pair design. You'll get a smaller loop area and less noise.

Noise picked up by antenna/power cable

If it's not in the patch cables, the noise may be coming in through your antenna. Plug all your patch cables back in and unplug your antenna. If the noise goes away, try an antenna noise suppressor. This filter plugs in-line between your receiver and your antenna, breaking the ground path between them. If you still have noise after unplugging the antenna, it may be coming in through the amp's main power cable. Try thicker cable.

Radiated noise

If it's not the antenna, try pulling the receiver from the dash while a tape or CD is playing. If the noise goes away, it's being radiated into your system. Try using magnetic shielding foil (also called Mu-metal) to shield the back of the receiver or wrap the wire or component (such as a digital clock) that's radiating the noise into your system.

Noise in speaker wiring

Noise can also come in through the speaker wires. To test them, turn the system off and disconnect the speaker wires from the amps. Now start the car. If the noise is still there, then it's being radiated into the speaker wires. Reposition them, or, as a last resort, shield them by wrapping them with Mu-metal foil.

Noise from electrical system

If you've tried all of the noise-fighting tips above and you still hear the noise, the problem might be with your vehicle. You might simply need to fill your battery with fluid. If that doesn't help, have a mechanic check your alternator and battery.

If your car is older and hasn't been tuned up recently, you may have ignition noise. It's a ticking noise that varies in speed as you accelerate. You may need a tune-up involving resistor-type spark plugs, shielded carbon-core spark plug wires, distributor cap, and coil.

If the noise doesn't disappear, then your ignition system may not be grounded well enough and is broadcasting ticks to other items such as your air cleaner, hood, exhaust system, etc. Chances are, grounding one of the under-hood components will eliminate the noise.

A very effective fix for electrical system noise is called "The Big Three" upgrade. This is where your vehicle's battery charging wire and chassis ground wires are augmented by adding large gauge wires (1/0- or 4-ga.) to those connecting the alternator to the battery's positive pole, the battery's negative pole to the chassis, and the chassis to the engine block. This establishes better current flow and more consistant voltage, which improves your system's signal to noise ratio. It also ensures against loose or restrictive ground connections, which, as said before, are common sources of noise.

Our tech support department is ready, 16 hours a day, 7 days a week, to help you sniff out the noisy component in your system (please have your Crutchfield invoice handy when you call).

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