How To: Reduce Humming Noise in a Car Stereo System

In this post, I am going to outline how to fix a high pitched whining noise in a car stereo. I have had issues with sound quality in my car stereo and I went out to find the answer to resolve my problems.

The Issue:

The car stereo sounded great but there was a high pitched whining noise when the car was “on”. It was loud and interfered with the sound quality of the stereo. This can be caused by a few things, but most likely by the interference of the electrical waves from the car’s power systems. There are multiple noises that can be causing an issue. In my case, I was able to drill down my issue to “ground loop noise” and “low-quality RCA cables”. 

Common issues that cause a high pitched noise in audio systems are:


  1. Loose wire connections somewhere in the system
  2. Ground Loop Noise (Improper Grounding of Negative Wire)
  3. Electromagnetic Interference (ex: Power cables running alongside RCA cables)
  4. Low-quality RCA cables
  5. Low-quality power cables 


The first step is to figure out which issue you are dealing with, by methodically going through the potential root causes one by one.

I would start in this order:

  1. ID the type of noise in the system
  2. Loose wire connection somewhere in the system
  3. Ground Loop Noise
  4. Electromagnetic Interference
  5. Low-quality RCA cables
  6. Low-quality power cables 

1. ID the type of noise in the system
  1. Turn the vehicle off, but keep the key turned so that the accessory power is on.
  2. Pause the music that is currently playing. While the music is paused, turn the volume 3/4 of the way up. Again, there is no need to send audio through the speakers at this time.
  3. Cycle through the modes, AUX, Standby, FM, AM, CD, etc. and take note of whether the hum or buzz was present. If it changed based on the input. That could give you insight on what to try to fix. For example, if the noise occurs only on your AUX setting, then it could be your 3.5 audio connector or cord you use to hook up your phone. Replace the cord. If the noise is on every input, then you know it’s not based on the input accessories. 
  4. If no hum or buzz was present, turn the vehicle ON and repeat steps 1-3 to try to isolate the hum or buzz noise in your audio system.
  5. Rev the engine while keeping the music paused, and just listen to see if the pitch or intensity changes when you rev the engine. If it does, then you can take the below steps to help remediate these issues. There are multiple causes and fixes for electrical issues, these are some common ones.

2. Loose wire connections somewhere in the system.

There are a few places that you could have loose wires:

  • Amp
  • Battery
  • Head Unit

Amp: Check the wire connections at the amp to ensure a tight connection. There are several types of wires going to your amp. Power wires, RCA wires, and Speaker Wires. They all must be on the correct input on your amp and tightly secured.

Battery: Pop the hood and locate your battery. Inspect the + positive terminal post. Ensure all the wires are firmly connected to the Positive post. A remedy for any issues at the battery would be installing a high quality power distribution block. 

Head unit: based on your installation ability, you can try to check the wires at the back of the head unit. Make sure they are all securely connected if you are able to, if not, try the other steps in this post before you take it into an audio shop. If you do go this route, I highly suggest a “mom and pops” shop vs a name brand store like Car Toys.

Do not go to Car Toys

I strongly advise against ever getting your car serviced at Car Toys as noted in my Google review of Car Toys, Plano, Texas location. They suck.

3. Ground Loop Noise.

This is caused by the improper Grounding of Negative Wire somewhere in your system. This tends to be a popping noise after an interval of time, basically, however long it takes electricity to move throughout your system and then ground out somewhere in the vehicle.  There are only a few places that it could be.

Battery: The negative terminal of your vehicle battery has a wire that terminates on the chassis. This is done generally at the creation of the vehicle. ) Ensure it is securely touching against the chassis as well as the battery box.

Amp: Locate the power wires at your amp. The ground wire will generally be black, while the power wire will generally be red or white. When properly installed, the ground wire will go from the back of your amp to the chassis of the vehicle, somewhere as close as possible for the amp. The shorter you make the ground wire, the better.

Once you trace the ground wire to where it is mounted on your chassis, ensure it is completely touching and is tightened so that it makes direct contact with the metal. The installers should have sanded the area where it is mounted so that it is bare metal.

There are two places you can install a device called a “ground loop isolator” to help with getting rid of the excess electrical signals in your car stereo system. Depending on your inputs these two work best. You can use both in your system if you want. I suggest a high quality isolator like these:

4. Electromagnetic Interference

(ex: Power cables running alongside RCA cables)

It is uncommon but likely that your power cables to your amp are bunched together, or run, near your RCA cables. This is a classic no-no because you are introducing interference into an amplified system. You can remediate this by re-routing either your Power cables or RCA cables away from each other. This must be done for the complete length of the car, when possible to avoid any interference from the power cables.


5. Low-quality power cables 

You got your stuff in a kit and someone installed it and its buzzing. Well, your power cables *may* be low quality where they could not be sufficiently insulated to not cause interference with your audio system.

If you have not separated the Power cables from the RCA cables, like put them on separate sides of the car, then you need to do that first. Otherwise, you could get better power cables.


6. Low-quality RCA cables 

Cables made with low quality generally don’t have the proper shielding to deflect noise as it waves all around you. Investing in high-quality RCA cables ensures proper noise shielding, and increased sound quality in your system.

One thing you can do is put a filter on the RCA line to your amp. This is an easy way to reduce noise introduced in your system if you can not organically find and fix the issue. It is important to get but a quality RCA filter to effectively de-noise your RCA line.

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Kelsey Salman

Solution Architect

A photographer and drummer based in Dallas, he can often be found at dog parks and Major League Soccer stadiums around the United States. He is also an avid aquarist and the happiest guy around when the company’s good.