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Car audio noise suppression guide

Diagnosing and treating noise problems in your car audio system

Noise Suppression Guide

This guide will help you diagnose and treat problems with extraneous noise in your car audio system.

Dealing with static, whining, and buzzing

You've installed a new receiver or amplifier in your car, and now you have a noise problem. Noise in your audio system commonly comes in these three forms:

  • Radio static
  • Amplifier whine
  • Buzzing speakers

What can you do? The trick is to determine what the source of the noise is. 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.

Read over this article for some hints and explanations of what can cause noise in your system. Use it as a checklist, eliminating possibilities until you find the culprit. You can also use this DIagnostic Flowchart as a guide to walk you through the troubleshooting process.

And don’t forget – if you purchased your gear from Crutchfield, don't hesitate to call on our tech support team (have your Crutchfield invoice handy).

Noise and your new receiver

If you’ve just installed a new receiver, here are two quick and easy starting points:

Receiver with antenna lead, power, and ground

Noise in your receiver is often due to a poor ground wire connection or a poorly grounded antenna.

 

Is your receiver securely grounded?

Improper ground is one of the biggest causes for introducing noise into your audio system. Is the ground wire located near a noise source (like a heater, air conditioner, or computer)? Is the ground wire actually connected to the vehicle's ground? Since the antenna lead can act as a ground (thereby enabling a new receiver to operate without its ground wire properly connected), the antenna lead is frequently the source of noise problems.

Radio static can be caused by antenna noise

Check to see if you're getting noise on all sources — CD, auxiliary/USB, AM, and FM.
If the noise is present only on the radio, then it's most likely coming through your antenna lead.

Unplug the antenna. If the noise goes away, try an antenna noise suppressor (like American International's AS100). This filter plugs in-line between your receiver and your antenna, breaking the ground path between them, thus preventing noise from entering your system.

Antenna filter

An antenna filter, installed between the vehicle's antenna and the receiver, can minimize noise entering your system from a poorly grounded antenna.

 

Radiated noise

If the noise isn’t coming in through the antenna, try pulling the receiver from the dash while a CD is playing. If the noise goes away, it's being radiated into your system due to the receiver's proximity to a noise producer (like a heater motor or car computer). This is often referred to as “sideway noise.”

If the noise-causing accessory has a motor, a source noise filter can be installed on the accessory's power lead to minimize radiated noise. If the car computer (or other motor-less accessory) is causing the problem, move your receiver's wiring away from that accessory to minimize the radiated noise.

Try using magnetic shielding foil (also called Mu-metal) to shield the back of the receiver or wrap the wire or component that's radiating the noise into your system.

Engine noise and alternator whine

Noise introduced through the power and ground wires connected to your receiver is called engine noise or alternator whine. If engine noise is your culprit, you may hear a whining or clicking sound. Its pitch will usually vary with engine speed.

If this is the case, you can install an alternator noise filter on the power line between the battery and the alternator to minimize the problem. You can also install a noise filter on the receiver's power lead to cut down on signal pollution (American International's S15A (15-amp, 250-watt) or S25A (25-amp, 350-watt) filters, for example). Most often, however, alternator noise comes from a loose or intermittent ground connection. See the section below about noise in the electrical system.

Alternator noise filter

An alternator noise suppressor connects inline between the alternator and battery, and can reduce high-pitched whining noise that modulates according to engine RPMs.

 

Noise and your new amplifier

An amplifier can introduce noise into your system through a bad ground or through a poor mounting. Rubber grommets or feet can help isolate the amplifier from the chassis of the vehicle, a potential source of noise. If all else fails, install 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.

Amplifier connections
 

Where is the amp mounted?

Is it near something that could be radiating noise, like a rear-mounted tuner or computer? If so, unbolt it and move it away to see if the noise stops. Remove your patch cables. If you still hear noise, check to see if your amp is isolated from the vehicle's chassis. Any contact between your amp's metal casing and your vehicle's body could cause noise problems.

Check your ground wire

Is it securely attached to the vehicle's chassis with a good contact to clean metal? Your ground wire should ideally be 18" long at most — a longer ground wire can cause noise problems. Improper grounding causes most system noise problems.

Check your gain structure

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 CD and put your CD player on pause. Listen to the system with the volume way down, then way up. Put on music. If you hear hiss or static in either instance, reduce 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 okay — you won't hear it while driving.

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.

RCA noise

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.

Twisted pair patch cables

Patch cables with a "twisted pair" design help reject noise

 

As a last resort, a ground loop isolator (like PAC's SNI-1) can be installed between the receiver's preamp outputs and your amp to minimize this problem.

Noise and whine picked up by the power or ground cables

We discussed ground cables above, because that’s the cause of noise more often than not. If the noise wasn’t due to a poor ground or through the stereo’s antenna cable, it may be coming in through the amplifier's main power cable. Noise can be created by cable of insufficient gauge, so you might try thicker cable.

Ground loop isolator

If you cannot find the faulty ground in your multi-amp system, a ground loop isolator can help minimize the problem.

Multiple amplifiers can also create ground loop problems, which can usually be solved by grounding each amplifier with its own separate wire. If you are unable to locate the cause, a ground loop isolator (like PAC's SNI-1) can be installed between the receiver's preamp outputs and the amplifiers to minimize this problem.

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 the electrical system

If you've tried all of the noise-fighting tips above and you're still getting static, whine, or hiss, then 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. With your sound system on and the car running, try grounding each of these different components of the car. It's possible that grounding one of your car's components will eliminate the noise. If so, make the ground permanent with a braided ground strap.

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 consistent 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. Read our article about The Big Three for more information.

Noise and your nervous system

Noise problems can be very frustrating, especially when you can't wait to hear your new equipment. It helps to remember that you've just placed a very sophisticated piece of electronic gear (a new receiver or amplifier) in the middle of an extremely complex system — your vehicle's electrical wiring. Noise is just nature's way of telling you that something's out of whack. Just run down the list, eliminating possible noise sources until you find the problem.

Crutchfield Tech Support

If you bought your gear from Crutchfield, you could call Tech Support for free help troubleshooting your system. The toll-free number is on your invoice.

  • Joshua B from Crestmead

    Posted on 10/24/2022

    I've got a 2006 Mitsubishi Lancer sedan, I've got a sony headunit, a phoenix gold 4 channel amp and pioneer speakers front and rear and have a bad static buzz present when the engine is running and changes pitch with the rpm. I've checked earths and even created new earths to no avail, i can't figure out what's causing it. My speakers are brand new and i believe it's only the front speakers that have this horrible buzz through them. I've replaced the rcas to no avail. I'm really stumped on this one to what's causing it. The static buzz is present even with no audio playing.

    Commenter image

    Buck Pomerantz from Crutchfield

    on 10/26/2022

    Joshua, In order to solve a noise issue, you need to first locate the source by careful and logical testing. You can use our How to diagnose and suppress noise interactive flowchart for help with that.
  • Verlin Maughan from KEARNS

    Posted on 8/23/2022

    My wife has a ford fusion hybrid. Every time the gas engine comes on I get a rolling buzz in the speakers and I can't find it. I've checked my grounds and my rca cables are not near my power wires off the vehicle. I am running my rcas off the rear speakers with the stock head unit please help

    Commenter image

    Buck Pomerantz from Crutchfield

    on 8/26/2022

    Verlin, At present, we don't know a lot about installing aftermarket gear in hybrid and all-electric vehicles. Try running the amp's ground directly to the battery, instead of using the vehicle chassis. Or, it may be that you need to make your amp's power and ground connections at the 12V side of the vehicle's DC-to-DC converter and not the battery.
  • Danny from Galt

    Posted on 7/30/2022

    Hello, so I recently acquired a 2013 Civic LX sedan and noticed I only get radio static when the car is running, it's nearly perfect when the engine is off. The static doesn't change with engine rpm or anything like that, it's just present. Now these Honda's have their antennas integrated within their windows, the rear window in this case, and I should add it doesn't affect closer radio stations too much (I usually listen to a station that's about 30 miles away in which it gets static and I've never had this issue with other cars). I did try roughing a shark fin antenna which did show some improvement but I was wondering if there is possibly a direct cause for the static when the car is running.

    Commenter image

    Buck Pomerantz from Crutchfield

    on 8/1/2022

    Danny, Try our interactive flowchart to pinpoint the cause of your noise and the possible ways to combat it.
  • Gerald V Johnson Jr from Henrico

    Posted on 7/26/2022

    Please Help. I'm running out of Ideas.... Okay I replaced my factory unit with an aftermarket unit from China. It's a plug n play unit and it only has one pair of rcas and one rca for the subwoofer. So I'm using a skar 7 band equalizer as my outputs for my 3 amplifiers in using. I independently grounded my equalizer to the chassis at first to see if it would help but it did not. Then I independently ground the aftermarket radio to the chassis and it still there. I also have a 2nd battery in my trunk and my amplifiers are receiving its power and ground source from it. The 2nd Battery is grounded to the chassis but it's not alot of grounding options on a 2020 Nissan Altima S model. I haven't tried a ground isolator just yet I'm trying to see if the problem can be eliminated.

    Commenter image

    Buck Pomerantz from Crutchfield

    on 7/26/2022

    Gerald, Try using our diagnostic noise suppression interactive flowchart to find and resolve your issue. Although, given the amount of gear and complexity of your system, you probably should hire a professional car audio installer to fix any problems.
  • Cory from Saint Charles

    Posted on 5/20/2022

    I've got an older Airstream motorhome, and the left channel has very little sound compared to the right. To make it more complicated, when the camper is powered by shore power vs engine, the buzzing gets much louder in the left channel. I unplugged all the left speakers and put a new jbl speaker (purchased here) up front in the left channel, and it has the same issue. Sometimes it'll have a split second of working. I'm think the head unit is bad but need to hear it from someone else. I was really looking forward to using the cassette player! Thanks

    Commenter image

    Buck Pomerantz from Crutchfield

    on 5/24/2022

    Cory, RV systems are often challenging, to say the least. You changed the speakers and the problem didn't go away, so you know it isn't the speakers. For troubles that come and go - try looking for a loose connection. Otherwise, it sounds like the old receiver/cassette player has played its last mix tape, and needs replacing.
  • Martin from Sunnyvale, CA

    Posted on 4/15/2022

    In my 2005 Boxster S.I have an Alpine head unit.that goes to a Clarion EQ.that goes to an Infinity amp.Im getting an engine whine(that changes with the RPM).But im only getting the whine on my front speakers.Which are your JBL tweeters in dash.an stock mids in doors.i believe theres a stock crossover between them somewhere.I tried the PAC SNI-1.that made it worse.Strange its only on fronts speakers.Maybe crossover is causing prob.Any ideas what to try next?? thanks

    Commenter image

    Buck Pomerantz from Crutchfield

    on 4/18/2022

    Martin, The kind of noise you describe usually stems from a loose ground connection somewhere in the system. And the number of components you have in your system will make it a challenge to find. Start by disconnecting devices to see if you can pinpoint the source of the trouble.
  • Adam Everett from Frederick MD

    Posted on 1/7/2022

    I recently installed led headlights in my 03 jeep TJ. They have running lights so I installed a switch in the stock switch panel. The jeep has a amp under the driver seat. I get a very annoying squeal in all audio sources only when my running light switch is flipped on. Using things like windshield wipers and blinkers change the pitch of the squeal. When I flip the headlights on the squeal goes almost completely away. What should I do? Thanks

    Commenter image

    Buck Pomerantz from Crutchfield

    on 1/7/2022

    Adam, It sounds like your LED lighting system is putting out interference noise that plays throughout your vehicle. You might want to check with a lighting company for an EMI filter that'll work for you.
  • Roberto from New jersey

    Posted on 12/4/2021

    After connecting a kenwood ddx9905s on a 2012 chevy camaro everything works good but only when I conect to Bluetooth I have this static noise a I've called customer service and I've been told os the ground problem but is the same ground that it was originally with the old radio any ideas

    Commenter image

    Buck Pomerantz from Crutchfield

    on 12/6/2021

    Roberto, Most noises are due to a faulty ground. Try rewiring your receiver's ground, using the harness wires, chassis connection, or some other combination.
  • Matt Tillson from McKinney

    Posted on 12/1/2021

    I just installed a new head unit as well as added a sub and 2 pairs of 6 1/2 kickers powered by a new amp. Im getting buzzing but just in the speakers connected through the amp, not the factory speakers powered by the head unit. I unplugged the RCAs from the amp and the sound goes away. Would I just need a ground loop interuptor?

    Commenter image

    Buck Pomerantz from Crutchfield

    on 12/2/2021

    Matt, You've taken one step in pinpointing your noise problem. The next step would be to plug the RCAs back in the amp and unplug them from the receiver and see what happens. For more help troubleshooting a noise issue, check out Diagnosing and suppressing noise.
  • Peter Goranites from Portland maine

    Posted on 10/6/2021

    help.. help..!!! 1994 Porsche 968 original radio with cassette player. Noise in radio that gets worse when you start driving. Also, no sound from one side, distorted on the other. I am not a car guy. Live in Portland Maine. In July, 2021 I paid a audio store $130 for a bench check, and then another $550 because he said problem is with radio that could only be repaired by sending it away. Got the radio back, same problem, brought it back, now he has had the radio since September and he keeps saying the repair shop that he will not identify is waiting for a part. After reading this article I am terrified that I am getting ripped off. Does your company have a repair instillation facility near me, or can you recommend one..perhaps for a whole new system.

    Commenter image

    Buck Pomerantz from Crutchfield

    on 10/12/2021

    Peter, It sounds like your 27-year old factory radio died, and you found out the hard way that repairing a factory radio is expensive as well as often impossible. Give us a call, so an Advisor can help you pick the perfect upgrade gear for your car.

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