Air Purifier making Noise (8 Noises + Fixes)

Your air purifier is making some noise and you wonder whether that noise is normal or not?

Then, you’re in the right place!

In this article, we’re going to check the different noises air purifiers can produce and what you can do about them.

Some noises, for example, quiet humming are normal. However, loud buzzing, screeching, or even banging noises can even indicate that something dangerous is going on inside your air purifier and it needs repair.

My name is Daniel, I am an electrical engineer, and I’ve worked in an electronics repair department of a large electronics factory. So, I’ve encountered quite a bunch of strange noises.

The most ridiculous one is the capacitor squeal, which makes electronic devices sound like a crying baby. This sound can occur in air purifiers.

So, without further ado, let’s have a look at the different noise types.

Summary: Is my air purifier’s noise dangerous?

Here’s a quick summary of all the noises listed in this article and whether the noise is dangerous and needs to be fixed.

Of course, you can do something about any noise listed here. So, just because I tell you the noise is not dangerous, doesn’t mean you should do nothing about it.

Now, I’d suggest you find out which of these noises best fits your air purifier’s noise. Once you got it, let’s continue with the investigation!

I will start every noise section with a short explanation of the noise, including potential causes. After that, we’ll check how to test for the different causes and fix them.

1. Loud fan noise

The most common noise in an air purifier, is, of course, the noise coming from the fan. The fan is the only moving part in your air purifier.

And anything that moves, makes noise. Consequently, most of the noises in an air purifier have something to do with the built-in fan.

A loud fan noise is not necessarily something unexpected.

Air purifiers force air through the filter, which excites the filter membranes. We perceive this vibration as noise.

Remember this: Any air movement creates noise. There is no air movement without noise.

Potential cause: Too high airspeed setting

The noise of an air purifier increases exponentially with the airspeed setting. Measurements show that air purifier power consumption doubles with each fan speed level.

Accordingly, noise doubles with each increase of airspeed.

How to fix it

Your air purifier has a display or indicator lights that represent the current airspeed level. Reduce this setting.

Potential cause: Clogged filter

An air purifier filter’s efficiency reduces by 50% after about 160 days of running. This means you should replace your filter twice a year.

If your filter is clogged, it could increase noise levels depending on how your air purifier controls fan speed.

If your air purifier has an adaptive fan speed control, it tries to rotate the built-in fan at a certain speed.

If, however, dust clogs the air filter, the built-in fan can not reach that speed, so the power control increases fan power.

As a result, your air purifier increases the force with which it presses air through the clogged air filter.

Likely, your air purifier is louder than it needs to be.

How to fix it

Fixing it is very simple. Depending on the air purifier model you have, get a good replacement filter.

Then, open the bottom or backside of your air purifier, take out the old filter, and put in the new filter.

Potential cause: Air purifier placement

The geometry of walls or furniture around your air purifier can amplify the sound coming from it.

If placed in the worst spot possible, e.g. in a cone-shaped corner of your room, all noise coming from the air purifier is forced in one direction (into the room).

And in the worst case of the worst case, the air and walls around your air purifier are arranged perfectly to match the air purifier’s acoustic impedance (a kind of air resistance), making it even louder.

It’s similar to having the ideal-sized hammer for a specific nail. 

That’s the same effect that makes many instruments, such as horns and tubas, work.

How to fix it

Place your air purifier in the center of your room. Air purifiers work best if they stand freely in the center of a room since this creates ideal airflow.

Also, sound waves bouncing off the walls cancel each other out.

Your air purifier should be quieter standing in the center of your room.

I did a quick experiment on this:

2. Humming noise

Humming noise in an air purifier is relatively normal. I can’t really think of anything dangerous causing it.

But you can reduce it! Let’s have a look.

Potential cause: Airspeed setting matches your room’s resonance frequency

Humming noise is often caused by the vibration of your air purifier fan matching one of your room’s resonance frequencies.

For example, a typical air purifier fan rotates at the following frequencies:

The lowest frequency humans can hear is 20 Hz. 

“Humans can detect sounds in a frequency range from about 20 Hz to 20 kHz”

Neuroscience. 2nd edition

So, according to the table, an air purifier can only create an audible humming noise if it’s at a high fan speed setting.

If, by accident, this frequency matches a resonance frequency of your room, the humming noise is amplified.

How to fix it

To reduce the noise coming from your air purifier, place it on anti-vibration pads (click here to view them on amazon).

Anti-vibration pads absorb the vibration from your air purifier and prevent it from resonating with your room.

You should hear a considerable difference.

These anti-vibration pads are good for larger air purifiers. For small air purifiers, an anti-vibration mat might be better (since it’s easier to balance on).

3. Crackling noise

Crackling noise is an interesting one. And it’s got a funny backstory (for me at least).

When I got my first air purifier, I turned it on and it started crackling.

I thought the crackling was normal. After a couple of minutes of running the (crackling) air purifier, I wanted to explore the air purifier’s settings and find out how to replace the filter.

When I opened the bottom part of my air purifier, the new filter was still sealed in plastic foil!

That’s what caused the crackling!

Potential cause: Sealed filter in your new air purifier

New air purifiers contain sealed filters. And, when I think about it, it makes sense.

After all, air purifier companies don’t want someone to buy an air purifier, and then return it with a used filter (filters cost money).

With the sealed filter packaging, an air purifier company ensures that the filter you get is new and not used.

Of course, before you run your air purifier for the first time, you have to know that you have to unbox the filter as well.

Ironically, the plastic packaging renders the air purifier totally useless, since the filter can’t filter anything then.

And I bet there are people somewhere on the planet running air purifiers with sealed filters, not knowing they have to remove them…

How to fix it

Before you run your new air purifier, remove the air filter’s plastic packaging. There should be no crackling noise afterward.

Potential cause: Dirt or sand trapped around the air filter

Another thing that can make your air purifier crackle is dirt or sand in the filter component.

Depending on how your air purifier is built, the air stream inside it could cause large particles such as sand or dirt to go in circles creating a crackling sound.

There are many ways this can happen, such as crumbs from your evening snack falling into the top opening of your air purifier when it’s turned off.

Or clipped pieces of fingernails flying into the air purifier.

How to fix it

Open your air purifier take out the filter and vacuum the inside of your air purifier to remove all these large particles.

4. Whistling

If you hear a whistling sound coming from your air purifier, something is definitely going wrong.

Whistles naturally occur when air blows over a sharp edge, which causes the edge to vibrate at its resonance frequency (source).

Air purifiers never whistle on their own. Of course. There are no sharp edges your air purifier blows air over.

Here are some reasons:

Potential reason: Hole in the air filter

There might be a hole in your air filter. The air filter naturally is a resistance for the air to pass through.

If there is a hole, all the air tries to pass through this narrow space, at extremely high speed (according to Bernoulli’s principle).

This can create a whistling sound.

How to fix it

The best way to fix a hole in your air filter is to replace it with a suitable replacement filter for your air purifier model. 

Alternatively, you can probably also stitch the hole with a piece of cloth. But that’s a lot of work for little gain. And imperfect stitches will reduce the filter’s overall efficiency.

So, I recommend just getting a new one.

Potential cause: Something sharp trapped inside

Whistling (just like crackling) can come from something trapped inside your air purifier. Whistling is a typical sound you can create with paper, by blowing right at the edge of a sheet of paper.

So, there might be a piece of paper, plastic, or something else that’s sharp trapped inside your air purifier.

How to fix it

Open your air purifier, take out the filter, and check whether you see anything inside your air purifier.

If you don’t see anything, you can also turn on your air purifier without the filter and check if the whistling persists.

If it does, continue opening the purifier until you find the cause of the whistling. And if there is no whistling when you run your air purifier without the filter, there might be something wrong with the filter instead.

Potential cause: Capacitor whistle

Here’s one more thing that can cause your air purifier to whistle. This cause is not related to airspeed.

Capacitors on the built-in electronic circuit board can whistle.

A capacitor is basically a rolled-up piece of metal, with insulation between the layers. When you apply alternating voltages to your capacitor, it expands and contracts slightly.

If you use a capacitor within its voltage specification, you won’t hear a thing.

But if there’s a fault in the electronics, one of the capacitors inside your air purifier might receive too high voltages and whistle.

How to fix it

To fix a whistling capacitor, you have to disassemble your air purifier until you get to the electronic circuit board.

Listen to where the whistling comes from and you should be able to spot a broken part on the circuitry.

After working in an electronics repair department, my number 1 tip for troubleshooting electronics is just to stare at them for 5 minutes.

This might sound weird, but 90% of the issues are visible. There could be

• a broken-off part
• a blown part
• burn marks

Look out for those.

If you find something, get the right replacement part online or in an electronics shop. Likely, you have to replace the broken part by soldering.

If you can’t see anything off, yet you still hear whistling from the circuitry, locate the whistling part and measure voltages around it.

Compare the measured voltage with the voltage rating of the whistling part and trace the overly high voltage to its origin.

If you’re not able to do these fixes, skip to the last section of this article “What to do if you can’t fix it”. You can fix these issues with a simple trick.

5. Scratching

Scratching sounds always come from a moving part scraping along another part’s surface.

Potential cause: Broken fan blade

Depending on the type of fan inside your air purifier, the fan blades might be more or less fragile.

It could be that your fan blade broke. This usually doesn’t happen on its own.

Either you run your air purifier for very long times (years on end), or you did not insert the filter properly and the fan scratches along the filter’s surface.

How to fix it

Open your air purifier and check the fan blades and your air filter.

If either of them is broken, replace it. Replacement fans might be hard to get, but you can harvest parts from broken air purifiers.

Potential cause: Wasp nest inside your air purifier

Wasps build their nests anywhere. And air purifiers (if they are turned off) offer perfect shelters for wasps.

So, if you don’t run your air purifier for some time, there could be wasps inside it. Especially if you store your air purifier in an outdoor shed.

How to fix it

Open your air purifier and check its inside. Remove anything that blocks the fan.

If you really find a wasp nest, replace your air purifier’s filter. Likely, it has many holes or dirt on it.

Potential cause: Fan bearings broken

Broken bearings create scratching noises! Normally, bearings don’t break on their own.

Average fan bearings have an expected lifespan of 50,000 hours.

So, either your air purifier is very old and the bearings indeed broke due to heavy usage. Or your air purifier took fall damage.

How to fix it

To fix broken bearings, you have to take the fan out of your air purifier and disassemble it until you can access the fan’s bearings. Also, check the fan’s rotational axis for faults while you’re at it.

Fan bearings are usually cheap to get. Even better would be to replace the entire air purifier fan with a matching one.

However, depending on the air purifier brand, these fans may be custom and hard to get by.

You can harvest a fan from a broken matching air purifier model instead (you can find broken air purifiers online, on Craigslist, eBay, or some other marketplace).

6. Buzzing noise

Buzzing noise always indicates that something is wrong with the air purifier’s power electronics.

That’s the electronic component receiving power from your wall outlet.

Potential cause: Too high voltage on wall outlet causes transformer buzzing

There might be a fault in the wall outlet you use, such as a grounding issue. These can cause a voltage overload.

Your air purifier’s built-in power electronics (including the transformer) can start buzzing.

Actually, transformers always buzz. However, if used within its voltage specifications, a transformer’s buzzing is very quiet. So you can’t hear it.

How to fix it

First of all, try running your air purifier off a different wall outlet. Ideally, it should be a wall outlet in a different room, on a different floor, or even in the garage.

The farther away it is, the better. This way you ensure that you use a different electric circuit from your house.

If it works there, that means something is off with the first wall outlet. Or even with the entire room’s circuit (you can try other wall outlets in your room as well).

In this case, I recommend hiring a technician to check the issue. Since this is about power electronics (and not a simple on-board circuitry fix in the air purifier), you should go the safe route.

Potential cause: Electric fault in the electric power component

Of course, the buzzing coming from your air purifier can also come from an internal electronic fault.

Transformers, capacitors, and inductors can all create buzzing sounds when there’s an issue with the electronics.

How to fix it

Open up your air purifier until you can see the electronic circuitry. Inspect the circuit board for visible issues.

If you can’t see any issues, use a multimeter to trace voltages. Listen to where the buzzing comes from.

Get the right replacement part and use a soldering iron to replace it.

7. Banging noise

Banging noises are incredibly rare in air purifiers. It has to be something related to the fan.

Potential cause: Broken fan axis

If the fan axis is broken, but the motor still tries to rotate it, there can be a banging sound, coming from the broken axis “jumping” around.

How to fix it

Depending on how the rotational axis’ material, you may be able to glue it. You can cold weld it using this J-B weld epoxy with hardener (click here to view it on amazon).

Although, admittedly, I doubt that the term “cold welding” is applicable here. Or at least it’s not scientifically precise. Still, this glue should be able to fix your fan!

Alternatively, either get a matching replacement fan (from a matching used air purifier). Or discard the air purifier entirely and get a new one.

8. Screeching / Whining noise

Screeching and whining noises usually have similar causes as whistling noises. Screeching is just like whistling but with a higher-pitched, harsh mix of frequencies.

And whining is like whistling, but with amplitude and frequencies changing over time.

Potential cause: Fault in a capacitor or inductance

Screeching and whining noises can occur in capacitors and inductances. Transformers are usually too heavy for screeching or whistling to occur.

How to fix it

Again, since this is an issue in the electronics, the solution is to disassemble your air purifier and inspect the circuitry.

Once disassembled, you can plug your air purifier into the wall outlet (be careful not to touch anything!) and listen to where the sound is coming from.

Once you locate the faulty part, find a matching replacement part online and replace it using a soldering iron.

If that doesn’t help and the new part starts screeching or whistling as well, the issue comes from a different part or a short circuit nearby.

In this case, you should trace voltages and look out for unusual values. Typical examples are zero voltage across a capacitor or a resistor without resistance (which means there’s a short circuit somewhere).

What to do if you can’t fix your noisy air purifier

Admittedly, you need electronics skills to do many of these fixes. And unfortunately, there’s no easy way out.

Or is there?

Here are a few suggestions if you can’t fix electronics:

Harvest replacement parts from used / defective air purifiers

If you roughly know where the noise is coming from, or which part is broken, you might as well buy a defective air purifier matching your model to harvest replacement parts.
Instead of fixing the circuitry yourself, your might as well simply replace it.

This method is very effective since used or defective air purifiers are easy to get online. And replacement parts are hard to get. So, just get broken air purifiers and use them as your replacement part source.

And if replacing entire components in your air purifier is not your thing either…

Sell your broken air purifier and get a new one

You switch sides and, instead of trying to fix your broken air purifier, simply sell it. Someone else will buy it from you and try to fix it or use it for replacement parts.

And you get a bit of cash for your air purifier.

Then, use that money to buy a new air purifier.

For your new air purifier, I highly recommend the Levoit Core 300 (click here to view it on amazon).

It is a very solid product. The built-in fan is indestructible. And it will last you for decades if you care for it!

Click here to read my full review: My favorite air purifier (review)