Have you been annoyed or freaked out by sounds coming through your speakers even when the car engine is off? You'd think that there shouldn't be a source of sounds when you turn off the car.
Little do you know that anything capable of generating an electrical field can impact the audio system.
Usually, the static noise comes to the speakers through wires with electrical signals. If you don't fix the patch cables, use magnetic shielding foil, or place grommets, other electrical devices inside or near the car will cause distortion in the signals, resulting in static, popping, hissing, or whining noises even if the engine is off.
In this guide, we're going to help you diagnose why are your speakers making a static noise when the car is off and treat problems with audio system noise.
By learning various ways on how to make your speakers quiet, you can end irritating static noises quickly.
What is Causing a Car Speaker's Static Noise?
To get a better idea of how to solve car speaker noise, you first have to understand how the problem originates.
Here are the different reasons why your car speakers are producing sounds even when the engine is off:
Electric Signals and Interference
Cables with electrical signals usually cause the speakers to emit static noise.
The distortion to the signal is often caused by signals from other electrical devices in close proximity.
In fact, even power lines, mobile phones, and anything plugged into the USB port can impact your car's signals.
Therefore, anything that produces or transmits an electrical field can affect the speakers.
This comes from radio frequency interference due to unshielded antenna cable or wire close to the antenna, putting out electromagnetic interference.
At times, the problem may come from radio accessories like a built-in CD player.
Low-quality wiring between the speakers and the radio can also produce strange sounds.
Radio Receiving Power When Car is Off
If you can still turn the car radio on despite the key out of the ignition, then that means the radio has constant access to a power source.
A poorly grounded radio, which means the wires are not appropriately fitted, creates a lot of static noise.
Antenna lead can serve as a ground, thereby enabling the receiver to operate without the ground wire being properly connected.
Stereo Noise from a New Amplifier
Bad ground or mounting of your stereo system's new amplifier is another possible cause of the noise.
How to Fix Speaker Noise Even When the Car is Off?
There are several ways to fix the source of speaker noise. Although just like in people, the first step involves identifying the source of the problem to find the appropriate solution.
Here are the best ways to deal with the speaker noise:
Track Down the Source of Static Noise
The first solution to everything is locating the source of the noise. Determining the cause lets you decide whether you can solve the problem yourself or a professional mechanic must interfere.
Do a quick test to work out if the radio unit itself is causing the noise. Turn on the head unit and set it up again to hear the static noise well.
- If the noise stops abruptly = issue may come from the speakers
- If the sound fades away = issue may come from the radio unit
Use a Circuit Tester
Optimizing a circuit tester enables you to diagnose the issue yourself properly.
Additionally, it allows you to work out if the radio has been incorrectly wired up.
In this way, you can ensure that the radio is not getting power from the ignition wire.
If you found that the ignition wire is transmitting power to the radio, it's best to ask a specialist to rewire it correctly for you or replace the speaker altogether.
Check the Patch Cables
Did you know that RCA patch cables linked to the car audio components can pick static noise? To test this, you must disconnect the cable from the amplifier.
Then, insert either side of another patch cable into the right and left input jacks of the amplifier.
Turn on both the engine and audio system. If there are no sounds, link the cables to the amplifier and detach it from the receiver.
If there's still noise, it's likely that the patch cables are picking up the static noise.
You can easily fix this by re-routing the cables and splitting them up from the power cable by at least 18 inches. However, this means buying new sets of patch cables.
How much noise the cable induces depends on the size of the loop area. The larger the loop area, the more vulnerable the cable becomes to receive interference.
For this issue, it's advisable to replace your old cable with a twisted pair design to get a smaller loop area and less noise.
If you want to keep the old cable, you may consider installing a ground loop isolator between the amplifier and the receiver's preamp outputs.
Utilize a Magnetic Shielding Foil
Static noise may be radiated into the audio system. You can verify this by pulling the receiver from the dashboard while playing a tape or CD.
If the static noise fades, then the static noise is being radiated into the car sound system.
Likewise, the foil will wrap the component that could be radiating the static noise into the system.
If the noise-causing accessory has a motor, place a source noise filter or move the receiver's wiring away from the accessory.
Fix the Speaker Cone
If you hear buzzing sounds aside from the static noise, there's a chance that there's an issue with the speaker cones or the surrounding parts.
Remove the front of the speaker and check how the inside looks. The cone is a vital component of the quality of sound.
Hence, you need to buy a replacement cone to fix the bent or damaged one.
Install an Antenna Noise Suppressor
First, check if there's noise on all possible sources such as USB, auxiliary, CD, AM, and FM.
If the sound originates on the radio, it's possible that it's coming through the antenna lead. To fix this, unplug the antenna.
If the static noise vanishes, only then can you try to install an antenna noise suppressor.
This helps filter and break the ground path between the antenna and the receiver, and consequently, block noise from disfiguring the audio system.
Use an Alternator Noise Filter
Noise coming from the ground and power wires linked to the receiver is called alternator or engine whine.
If this is the case, install an alternator noise filter between the battery and alternator to help minimize signal pollution.
If the issue persists, there might be a more significant problem with the vehicle's electrical system.
Similarly, if the car is old and hasn't been turned for a long time, the ignition may be causing the static noise.
Disconnect Speaker Wires from Amplifiers
There are cases wherein the speaker wires are the culprits for static noise.
In general, the wires should be firmly fitted, and there are no breaks in the wireline, nor should there be lying power cables or high frequency lines.
To test the wires, turn off the audio system and then detach the wires from the amplifiers.
If disconnecting doesn't work, it's possible that the cable with inadequate gauge is causing the noise. In this case, try using a thicker cable.
Place Grommets or Add Large Gauge Cables
If the wires are fine, an amplifier with poor mounting may be the potential source of speaker noise.
Grommets or rubber feet can isolate the amplifier from the car's chassis, which acts as a potential source of the noise.
If grommets are not working, try adding large gauge cables to connect the alternator to the car battery positive pole.
After that, link the chassis to the negative pole, and then the chassis to the engine block.
This results in a consistent voltage, and subsequently better current flow. As a result, you improve the system signal to cut noise.
Check Other Car Components
If you've tried all the above fixes and nothing seems to be working, your vehicle may be the one causing the static, whining, and hissing noises.
You can solve this by filling the battery with fluid. However, start by diagnosing whether you hear tickling sounds.
If you hear this, you need to tune-up with shielded carbon-core spark plug wires, resistor-type spark plugs coil, and distributor cap.
If the static noise is still present, there may be poor grounding broadcasts to other components like the exhaust system, the hood, and the air conditioner.
Try grounding one of the components to eliminate the noise.
Hearing a noise from your car's audio system could mean there's a signal interference or poor grounding.
Remember that the first step is locating the source of the sound, then finding the appropriate solution.
Make sure to insulate all broken wires when you handle the problem on your own. If you need assistance, it's always good to consult with an expert technician.
Jessica is a Acoustical Engineer, currently based in the San Francisco Bay Area in California. After graduating from her degree in Master of Engineering degree in Acoustics from Solent University in 2014, Jessica worked for a few companies before She will be blogging about her past and current experiences in the studio and sharing her journey as she pursues her career goals. She enjoy the balance of work inside and out of the office, solving practical problems on a daily basis as every project is different and requires a different solution, the variety of work (sound insulation testing, background noise survey, mechanical plant commissioning, external plant assessment, plant room breakout assessments) and the mix of independent and team work.