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AC adapters power up or charge the electronic devices we use. Since they are responsible for delivering power to our devices, it can be worrisome when an AC adapter makes noise. So, why do some of them make noise, and is there anything you can do about it?

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8 Sources of Noise in AC Adapters and When To Be Worried

The noise you hear from your AC adapter can be caused by multiple reasons, some of which are perfectly normal and others that indicate a problem you should look into. Let’s explore these reasons.

1. Electrical Noise

All AC adapters produce sounds in the form of electrical noise. However, most people don’t hear them because they’re high-frequency and thus inaudible to humans.

The average human can detect sounds with frequencies between 20 Hz and 20,000 Hz. Any sound with a frequency outside that range requires exceptional auditory perception to hear. Some people, especially older ones, will already have difficulty processing sounds within the normal human hearing range.

Given that all AC adapters generate some electrical noise, there’s a possibility that you only hear noise from your adapter because you have exceptional auditory perception. If that’s the case, then there’s nothing wrong with your AC adapter.

To give you an idea of the frequency that humans can detect, here’s a test tone for 20,000 Hz, which is at the higher end of the human hearing range:

If you can hear that sound, and it’s comparable to what you’re hearing from your AC adapter, then there’s a possibility that the high-pitched noise you’re hearing isn’t something you should worry about. It may be something that we don’t hear every day because electrical noises are inaudible, but they’re still within the range of normal operation.

If the noise you hear from your adapter is the electrical noise produced by all adapters, it means your AC adapter is functioning correctly. To know whether to be concerned about the AC adapter noise you hear, here are some things you should try:

  • Check all the AC adapters around your house. Listen to them when plugged in to check if they are making the same noise. If they are, you likely have exceptional hearing and can detect the normal electrical noise produced by adapters.
  • Ask another person if they can also hear the noise coming from the AC adapter. If they can’t, the AC adapter is probably in good condition and you only detect sound because of exceptional hearing.
  • Compare the sound you hear with the test tone we shared to see if it’s on the same frequency or higher.

If your ears can’t process the 20,000 Hz test tone we shared, but you can hear the noise from your AC adapter, it may still be a part of its normal operation. There are many reasons why AC adapters make audible noise. Some may require you to replace the AC adapter, but most are caused by the circuit design and don’t indicate performance defects.

Still, you must find the cause of the noise to determine whether you should replace or repair your AC adapter. Doing this will also help you avoid any potential damage that a faulty adapter can cause to your device.

2. Underpowered or Overpowered Outlet

If you’re using a defective power outlet that is underpowered or overpowered, your AC adapter may produce a continuous buzzing sound.

If you’ve recently noticed that your AC adapter is making noise, checking the outlet is an important first step. It will help you determine whether to attribute the noise you hear to your AC adapter or a faulty power outlet.

It is easy to rule out a faulty outlet because you only need to plug the adapter into another outlet. If the noise stops, you know that it’s the power outlet causing the noise, which makes it easier for you to address the problem because you know exactly which of the two needs your attention.

Now, if the noise comes from a faulty power outlet, you have two options to deal with it. You can use an outlet plug cover to prevent other people from using it or have it checked by an electrician to determine why it’s underpowered or overpowered.

3. The Circuit Design of an Adapter

The circuit design of some AC adapters results in the generation of audible noise. An AC adapter that produces noise due to its design will do so from the moment you start using it.

To avoid such noise, check an AC adapter before you buy it, as you’ll find this problem with specific products and not others. But if you’re already using such a product, the buzzing sound should not worry you.

However, if the sound gets louder over time, it could mean that you’re using a faulty adapter that needs replacement. Unfortunately, getting a replacement for the adapter from manufacturers can be challenging because they consider such sound to be within the bounds of normal operation.

We know some people who’ve had to live with the noise from their AC adapter because the manufacturer refused to replace it for them. You might have to explain to them that the noise is getting worse before they even consider sending you a replacement.

4. Switched-Mode Power Supply (SMPS)

SMPS uses a different mechanism to deliver power efficiently. It uses a regulator that continually switches between different modes to reduce the amount of energy wasted. Manufacturers use this mechanism instead of linear power supply when they need more efficient power delivery or a lighter power adapter.

SMPS makes it easier for manufacturers to build the adapters we need for modern devices like laptops. Despite being more energy efficient when compared to linear power supplies, SMPS is prone to generating electrical noise that is audible to humans. If you’re using SMPS for your device, it needs proper noise suppression to prevent it from making noise.

If this is what’s causing the noise from your AC adapter, it doesn’t mean that you’re using a faulty one. It simply means that your adapter doesn’t have proper noise suppression, which can also reflect its overall build quality.

5. Poor Noise Suppression in Low-Quality Adapters

Low-quality adapters have poor noise suppression and produce noises that can be difficult to ignore.

If you buy a low-quality adapter and find that it’s making too much noise, your best option is to buy a better-quality one. If the low-quality adapter came with a device you bought, you could ask the manufacturer for a replacement.

Some will claim that noises from the adapter are part of normal operation and won’t replace it. But others, especially reputable companies, will immediately send you a replacement.

6. Inconsistent Voltage Output

You’re likely to hear noise from your adapter if it’s faulty and prone to voltage fluctuations.

You can use a voltmeter to check whether the AC adapter you’re using has a consistent voltage output. When using the voltmeter, the reading should consistently remain within the output range and not fluctuate out of range.

When an AC adapter’s voltage output fluctuates out of range, it’s a sign that the capacitor is not working correctly. A faulty capacitor is a crucial issue you need to address immediately because it causes power inefficiency and may result in short-circuiting and permanent device damage.

Repairing an AC adapter with an inconsistent voltage output is doable if you have the technical know-how and tools to replace the capacitor. However, even the technicians we know would recommend replacing the adapter rather than trying to replace or repair the capacitor.

7. Lower Wattage Output Than Required

If you’re using a universal power adapter, there’s a possibility that its output is lower than what is required to power up or charge the device. Remember that AC adapters will also make noises when plugged into a device they’re incompatible with, so it would be best to check the wattage output before you even buy an AC adapter.

Contrary to what many believe, universal adapters aren’t “universal” in the sense that they work with any electronic device. If your laptop needs 45 watts, you can’t use an AC adapter with an output lower than 45 watts, even if it fits the power port.

To determine the wattage requirement for your device, simply multiply its voltage and amperage requirements. For example, if you’re using a laptop that needs 20 volts and 2 amperes, you need an AC adapter with an output of at least 40 watts.

The output can be higher than 40 watts because the adapter will adjust the power that your laptop gets. However, if it’s lower than 40 watts, the power adapter won’t have enough wattage to power up or charge your computer.

8. Damaged Cord or Adapter

If you’ve been using your AC adapter for a long time and it started to make noise only recently, it’s likely that you’re using a damaged cord or adapter. Electrical noises are common for AC adapters, even high-quality ones, but these noises worsen when the cord or adapter is damaged.

AC adapters have built-in noise suppression that helps eliminate all the electrical noises they produce. However, as you continue to use them, the suppression gets weaker, resulting in louder noises from the adapter.

It doesn’t mean that you have to replace your AC adapter immediately. However, it’s something that you may want to consider doing before your adapter starts to malfunction and cause even more significant issues with your device.

Frequently Asked Questions About AC Adapter Noise

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Is It Safe To Keep AC Adapters That Are Making Noise Plugged In?

You can keep most modern adapters plugged into a power outlet, even if they’re making noises and you’re not using them. They come with several safety mechanisms, so you don’t have to worry about them heating up or shorting.

However, if you were able to determine that the noise is coming from a faulty AC adapter, it would be best for you to remove it from the outlet whenever you’re not using it.

Doing this will save you from the painful high-pitched noise that it makes and help you avoid the possibility of overheating or a short circuit.

Can We Repair AC Adapters That Are Producing Abnormal Sounds?

You can repair AC adapters that are making abnormal noise. However, you’ll need the right skills to determine which part of the adapter is responsible for the noise. Aside from this, you’ll also need the right tools to repair the adapter.

If you consider the requirements to repair an AC adapter to eliminate its noise, getting a replacement might be a better option. You will find many different options in the market, and you can even find high-quality adapters for less than $20. It’s a small amount to pay, considering the relief you’ll get from dealing with a noisy adapter daily.

Is It Safe To Use a Universal Adapter as a Replacement?

Universal adapters are safe for any device if they have the output required to power up or charge the one you’re using. So you must know how to calculate the wattage requirement for your device and compare it with the AC adapter’s wattage output.

The adapter should also have a consistent voltage output that stays within its range to prevent electrical damage to your device. If the universal adapter you’re using has a voltage output that fluctuates significantly, it won’t be as energy efficient and may even be detrimental to your device.

Aside from this, you must ensure that you get it from a reliable brand. A high-quality adapter will help you power up your device safely and provide proper noise suppression to prevent it from making noise while in use.


It’s not common for us to hear noises coming from AC adapters, and it may even be alarming to many people. However, there are many reasons for it, most of which wouldn’t even affect its power delivery and reliability.