Why Do My Speakers Make Noise When My Car Is Off?

The radio is, believe it or not, an integral part of the car; maybe it’s not as important as the engine or the suspension, but it’s definitely vital to people who need to take long drives. For instance, if I were to have a job that required me to drive across the country for hours, or even across the city at night, I would need a way to stay awake. So, I always make sure that both my radio system and my speakers are in mint condition and working properly. And in all honesty, nothing is worse than having a set of speakers that make a lot of noise, especially if the car isn’t even running.

You probably came across this issue as well. For some reason, the speakers are giving off a weird sound, but the engine isn’t running, the battery is off, and you’re pretty sure you have everything hooked up properly. And while I did cover some speaker noise-related issues in the past, I think it’s time we looked into this noise problem in more detail.

Car speaker making noise when car is off.

What Types of Noises Do Speakers Make?

As we will see later, there are lots of potential sources for the speaker noise. So, in order to find these sources, you need to know your noises.

Generally, the unwanted speaker sounds, whether your car is on or off, fall into one of three categories:

  • Hissing
  • Buzzing
  • Whining

Both hissing and buzzing are essentially static or white noise, depending on the intensity. Whining is a little less common than these two, at least when it comes to parked cars, but it still happens and it can vary in intensity.

Potential Speaker Noise Causes

Cars are complex and any little thing can set off a noise. Most of the time, you’ll need to consult an expert and let them diagnose the root problem, which can take a while. However, there are a few speaker noise causes that appear more frequently than others.

Grounding

Grounding is by far one of the most common reasons behind speaker noise when the power is off. If you didn’t fit the grounding wire properly, the speaker will make loud, hissing static sounds when it isn’t on. The same can happen if the wire you’re using for the grounding isn’t thick enough.

I should note that this issue is exclusive to cars that aren’t moving. During the drive, the grounding won’t make any noise.

Speaker Wires

Your car radio is connected to the speakers with a series of wires. If these wires are damaged, worn, or of poor quality, they can produce weird noises even when the car isn’t running. The radio has a constant power supply from the car battery, so as long as it’s hooked on and it has bad wiring, you can expect some noises to follow.

Radio Still Receiving Power

Some radios switch off the second you pull the key out of the ignition or power down the vehicle. However, there are radios out there that you can turn on at any point; these radios have constant access to a power source. Therefore, you can expect some static or whining with or without ignition.

Electrical Interference

Most of the causes I listed above are “internal”, so to speak. In other words, they mostly have to do with components that are already in your car. However, with electrical interference, the source of the noise issue is mostly external.

Let’s say that you want to plug something into your car’s USB port or an auxiliary port, e.g.,your cellphone, your MP3 player, a power cable, or anything similar. All of these external devices can either transmit or distort electrical signals. Said signals interfere with the sound that comes from your speakers, so it’s natural to hear some whining or buzzing during a drive. However, the noise from electrical interference can also come when the car is off, though it’s not that common.

Interestingly, your car speakers and stereo can suffer from electrical interference OUTSIDE of the car. To put it simply, any device powerful enough to emit electrical signals can have an effect on the audio equipment. This scenario is also one of the most annoying ones, since you can’t really do anything about it if the signal is coming, for example, from a power plant or an electrical installation in someone’s home.

How to Get Rid of Speaker Noise

In order to get rid of the noise when your car is idling in your garage, you’ll need to isolate where the noise is coming from. I suggest you do the following:

  • Inspect the patch cables for any damages
  • While playing the stereo, remove the receiver from the dashboard
  • Disconnect the speaker wires from the amplifiers, then try switching the car off and look for the source of the noise
  • Inspect both your car battery and your alternator
  • Get a car noise filter or noise isolator if your engine is making the noise

Naturally, it would also be a good idea to check the speakers themselves. Any external damage to the speaker can cause the noise, so make sure to give them a thorough inspection; check everything, from the wiring to the cones. If all seems to be in order, proceed with the steps from the list above.

Check the Patch Cables

RCA patch cables tend to wear out, so it’s a good idea to test how they work. You do this by pulling one out and inserting a new, high-end cable in its place. Since there are usually multiple patch cables connected to the audio system, you might want to do this for each of them. After all, multiple cables can be out of order.

If you don’t hear any noise when performing this test, then the solution is simple. All you have to do is spend a few extra bucks to buy some high-end patch cables and replace the bad ones. I have to stress the “high-end” part, however; low-grade cables can produce noise even if they work properly, so make sure you focus on quality rather than price.

Disconnect the Wires

Poor shielding tends to be an issue with speaker wires. So, when you disconnect them from the amplifiers and hear no noise, you might need to use some magnetic shielding foil, or Mu-Metal. Wrap the shielding around the wires and try reconnecting them.

However, the issue with the speaker wires might not be related to the shielding. Sometimes, the wires might just be too close to other circuitry in your car. If that’s the case, simply try changing the position of the wires a bit.

Mu-Metal is also useful for stereos; when you remove the receiver from the dashboard and hook it up to play outside, it might play without any hissing or static. That’s your sign to use Mu-Metal shielding around the stereo itself before putting it back into the dashboard.

Battery and Alternator Issues

Usually, an alternator might whine when you drive or accelerate. But it’s still a good idea to have a mechanic look at it even if the whining noise is coming when the car isn’t moving.

Both the alternator and the car battery can generate electrical impulses that the speakers can pick up. And while a battery is easy enough to replace, with the alternator you’ll definitely need a mechanic. Have them tune your engine up and replace any faulty parts such as the spark plugs or their carbon-core wiring.

Solving the Grounding Issues

A typical grounding wire ought to be 18 inches long, at most. Any wire longer than that can produce noise. More importantly, it should be thick enough and be well connected to the amplifier. Loose or thin grounding will cause your speakers to hiss.

Noise Filters

I’ve run into more than a few mechanics who say that noise filters don’t really solve anything. In their words, it’s just putting a bandaid on an open wound. And while I do agree that you need to get rid of the problem outright, a noise filter is still a great temporary solution.

Most of the time, installing a noise filter is simple:

  1. Insert the coaxial plug into your radio’s stereo socket
  2. Connect the speaker’s RCA cables to the noise filter’s stereo socket
  3. If necessary, get an adapter cable with one stereo plug and two RCA cable sockets

A Few Words at the End

Car stereo noise is bad enough when you’re driving, but it’s an absolute nightmare when your car is just sitting there with the ignition off. However, if you manage to isolate the problem, you can rest easy knowing that there are no weird buzzes or whines coming from your garage or driveway.

Was this article helpful and did you manage to get rid of speaker noise from your parked car? Please let me know in the comments below.

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