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How to diagnose and suppress noise

An interactive flowchart to help you solve some common problems found in car audio systems

In the 1950's, I'd take the family television's vacuum tubes down to Willow Grove Radio and TV Repair, check them with the giant tester machine, buy new replacement tubes, and reassemble the repaired television, so my mom and dad could enjoy their precious, respectively, Dean Martin and Red Skelton shows. In the 1960's, I studied radio and electronics at the Franklin Institute in Philadelphia. After college, in the early 70's, I joined a rock 'n roll band as the soundman, learning how to operate the electronics that make music sound good. Then, I worked in a music store in Austin manufacturing, installing, repairing, and operating sound systems and components for recording studios, nightclubs, and touring bands. I moved back to Charlottesville permanently in 1984 and opened a little demo recording studio. I also attempted to put to practical use the creative writing degree I had picked up along the way. In 2006, I finally came to my senses and got this job at Crutchfield where they actually pay me to ramble on, rant, and explain the things I love about music, electronics, and getting good sound.

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Electrically speaking, your car is a pretty active place. Every piece of electronic equipment in your car, such as power windows, windshield wipers, and the alternator, generates its own small electrical field. These fields can be conducted through the metal that makes up your car's body and chassis. They're not really a problem until they sneak into the audio components of your stereo system and become noise.

Check all connections
You can solve almost all noise problems, without the need for adding noise filters, by making sure that every component is installed properly, that high-quality equipment (especially wiring and cables) is used, and that the car's charging system is working properly.

Loose grounds cause noise
Besides the stereo system, noise can also come from the vehicle's electrical system. Often, tightening or replacing a vehicle's ground cables will clear up the noise issue in the sound system.

  • Check the battery fluid level and fill, if necessary
  • Make sure the battery leads are tight to their posts
  • Make sure the battery's negative-to-chassis ground cable is sturdy, intact, and tightly secured

How to diagnose and eliminate noise
Use the following process to diagnose and cure the most common noise problems associated with systems with outboard amplifiers. The idea is to isolate the specific cause of the noise so you can eliminate it. For a more detailed explanation on how to eliminate noise, see our Car Audio Noise Suppression Guide. If these tips don't solve the problem, it's helpful to be able to call on Crutchfield Tech Support. If you purchased your gear from Crutchfield, or purchased tech support separately, you can contact them toll-free seven days a week.

Do you hear noise?

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Or view the full chart here

Noise Suppression Flowchart
  • Josh

    Posted on 3/26/2016

    This is very helpful, thank you!

  • sam

    Posted on 7/28/2017

    this looks awesome gonna run thru it as soon as i get home

  • Jason Mangen from Bowie

    Posted on 8/11/2017

    When I plug my iPhone lightning cable into the USB cord connected to to the iPhone slot in my Kenwood dnx773s receiver I get a buzzing sound in the speakers. All other audio is fine. What could be causing this problem?

  • Buck Pomerantz from Crutchfield

    Posted on 8/11/2017

    Jason, The first thing that comes to mind is to check and see if the USB cable has come loose from the receiver. Or maybe the cable is bad. If you bought your receiver from Crutchfield, you could call Tech Support for free help troubleshooting your system. Their toll-free number is on your invoice. If you purchased your equipment elsewhere, you can still get expert Crutchfield Tech Support - 90 days-worth for only $30. Click on this link for details.

  • Alex from Venice

    Posted on 8/26/2017

    Have a '14 Lexus ES. Very Loud bass noise after car shuts off. I've had a powered sub in my car for about a year with no issues. Recently upgraded to a more powerful amp and sub, (wired from the start with proper size wiring to accommodate a more powerful setup). Have a LOC to create preamp outputs and a remote wire to the amp. Also recently added a Ground Loop isolator in an effort to remedy the noise. Still does it. Have to disconnect the RCA cables from amp before shutting the car off. Please help.

  • Buck Pomerantz from Crutchfield

    Posted on 8/31/2017

    Alex, It sounds like your amplifier's remote turn-on lead is not connected properly to a 12-volt source that turns off immediately when the car is turned off. Many cars keep certain electrical circuits live for a few seconds after the ignition is turned off. You shouldn't use any of those circuits for your turn-on signal. If you bought your amp from Crutchfield, you could call Tech Support for free help troubleshooting your system. Their toll-free number is on your invoice. If you purchased your equipment elsewhere, you can still get expert Crutchfield Tech Support - 90 days-worth for only $30. Click on this link for details.

  • Jhampier Montes from Orlando

    Posted on 11/27/2017

    What is advise on connecting shield for terminals on a factory amp to aftermarket unit. I hear static I'm the radio. Using rca to avoid using amp and head unit together causing other issues

  • Buck Pomerantz from Crutchfield

    Posted on 11/27/2017

    Jhampier, Without knowing precisely what factory amp and "aftermarket unit" you're referring to, we can't help you with advice. If you want a question answered about a system, you must identify the gear by brand names and model numbers so we can get the right information to you.

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