Hearing a repetitive knocking noise from your exhaust fan is exhausting! Instead of enjoying your me-time in the bathroom while soaking in suds or reading a book, and more, that precious time will turn sour because the knocking sound spoils everything.

Bathroom exhaust fan knocking noise

Bathroom fans are of indispensable electrical appliances at home. For many years they have been a part of your HVAC system that maintains vent functions, keeps moisture building up molds and mildew, and releases odor away.

Just like any other home device, bathroom fans have a limited span of life. And when they underperform and make noise, we check and fix them before deciding to replace them.

Are Bathroom Fans Supposed to Be Noisy?

Bathroom fan noise should be easy to understand because nobody wants a noisy bathroom fan.

Yes, bathroom fans can be noisy, especially when they are worn out and have been there ventilating the bathroom for so long. Imagine the years of use, day in and day out; what would you expect?

Nothing lasts forever.

Okay, let’s get to the point if exhaust fans are supposed to be noisy, then nobody wants a noisy ceiling fan because a noisy fan is an indication of faulty ventilating appliances.

Ideally, any fan produces sounds. Different sounds pertain to varying noises.

When the sound becomes a loud noise, you need to worry because the noise level the bathroom exhaust fan creates has desired decibels.

Your exhaust fan should usually sound 20 to 40 dB. To illustrate this, a whisper or normal breathing is around 10 dB, the rustling of leaves 20 dB, and conversation tips to 50 dB.

And there are valid reasons why exhaust fans make different kinds of noise. Banging noise is one of them.

Let’s check them out.

Reason Behind Bathroom Exhaust Fan Knocking Noise

1. Broken Fan Blades

Broken blades are one of the most apparent reasons for the knocking noise.

Fan blades constantly spin when the unit is on, and it is entirely normal for them to produce sound. But when they make noise, as in knocking, grinding, or vibrating more than they’re supposed to, any of the blades could be broken or dented.

Next Read: Ceiling Fan Clicking Noise: 9 Easy Ways to Fix the Fan Noise

The broken part could have gone somewhere and caused the remaining blades to produce a clicking or knocking noise.

2. Faulty Motor

The heart of the machine causes the fans to spin.

A noisy motor means whirring or humming, sometimes vibrating and grinding; it’s worn out, old, and dying.

Faulty engines produce buzzing and humming sounds but don’t have the power to run the blades.

Check for this kind of noise, as it can result in overheating. Perhaps, loose or faulty wiring is at play.

Let an expert inspect the motor’s condition. If the damage is severe, it is difficult to remedy the issue but replace the motor or the entire fan unit.

3. Poor Mounting

The continuous motion of the fan blades shakes the whole unit causing the screws and brackets to displace in time.


Loosen parts add noise to the already damaged exhaust, such as banging, clicking, crackling, and knocking.

  • First, dismount the unit and put the pieces back again using undamaged screws to correct this issue.
  • Sometimes, broken screws let go and cause the fan housing to shake.

4. Insufficient lubrication

Machines like exhaust fans have parts that require routine lubrication.

Gunk-up motors, bearings, shafts, and screws need degreasing for the exhaust fan to run smoothly.

Unlubricated parts will cause the components to get stuck and produce a vibrating, grinding, or squeaking sound.

Help it run like new by applying oil or lubricant. Use the correct lubricant grade for your fan.

WD-40 lubricant spray is an effective grease and rust remover. Get recommendations from experts on what’s suitable for your bathroom fan.

5. Old exhaust fan unit

The average lifespan is around ten years. With good maintenance, your exhaust fan can extend up to 15 years. However, defective fans from manufacturers should be checked before installing a new one.

A brand-new unit will give you a more comfortable and peaceful bathroom experience than the old one because newer models have parts that don’t rust and are durable.

More Bathroom fan Noises and Troubleshooting

Bathroom Fan Humming Noise

A soft hum is expected, but an apparent humming noise could mean the bathroom fan is full of dirt or dust.

Dust will build up on the fan blades, shaft, and rotor, causing the fan to slow down.

Other sounds like buzzing or grinding indicate that the motor works harder to move the fans but is having difficulty creating energy due to the clog of dirt.

So, it is essential to conduct regular cleaning to keep the noise off.

It is best to disable the parts and clean them separately using a portable vacuum cleaner or an air compressor to reach the bathroom vent when cleaning.

Humming but Not Spinning

There is a problem with the motor. Call your repair guy to inspect the motor.

If it needs replacement, get one.


Or replace the entire unit as it is more cost-efficient.

Clicking noise

Could be a loosened screw, misaligned housing, or bent fan blade.

Dismount the parts and tighten the connections.

Check also for loose bearings.

Vibrating noise

Vibration noise is common for exhaust fans to produce, especially since they are designed differently from conventional electric with enclosed housing or fan guards.

The tight space housing the fan will cause the exhaust case to shake and vibrate. Over an extended period, this kind of shaking will rattle the screws and loosen them from the mounting.

Check on the screws and tighten them up after each cleaning.

Noise when windy

The mechanism of an exhaust fan is to release air through the exhaust pipe or port that goes outside the house.

This port’s end is a damper that will prevent the exterior air or wind from entering through that port.

Check that damper as it has fallen or been taken out by the strong wind, which causes the banging and flapping noise.

PRO TIP: Dampers control the inward and outward airflow and manage humidity and air temperature to keep the room free of stale air, mold, and mildew caused by moisture.

Also, strong winds will make the vents flap causing too much noise. Fixing the flapper can be done by:

  1. Replacing the flapper with a new one with a spring-loaded damper prevents the flapper from hitting the metal.
  2. Some dampers have rubber seals, so when the flapping closes, it will seal tightly.
    1. Grinding—This can also be because of the misalignment of parts. Check the fan blade the most, and don’t let the grinding sound persist without doing something to fix it. The grinding noise will cause more damage in other parts.
    2. Rattling—Rattling noise is the same as a vibrating sound but a little louder. Meaning the screws are not well tightened.
    3. High-pitched noise—The air duct or air vent may be struggling to release exhaust air outside, similar to the airflow in an air conditioner.

The added pressure will cause a whistling sound through the vents, and the noise is described as high-pitched because the air passage is limited.

The higher the air pressure, the higher the sound or pitch produced by the moving air.

Check the diameter size of the ductwork and the way it crawls outside to vent the air.

How to Fix a Noisy Bathroom Fan

  1. Clean fan and all moving parts

This is to ensure smooth function, oscillation, and coordination of parts.

  1. Adjust the fan blades

Replace broken fan blades, and re-attach the misalignment.

  1. Use Sorbothane rubber

Rubber is a perfect material for home appliances as a shock protector.

The elasticity and malleability of rubbers can fit the shapes of the materials they protect. This is best for reducing or dampening the noise produced by faulty exhaust fans.

PRO TIP: DIYers use Sorbothane rubber in damping materials to protect against vibration. It also serves as an acoustic insulator, such as earplugs. Sorbothane is elastic, viscous, and highly absorbent.

  1. Use larger ducts

Ducts with larger diameters will allow smooth airflow even if the ports are smaller. It is better to have larger ducts on smaller ports than larger ports on smaller vents.

  1. Lubricate the fan motor and blades

Lubricating oils maintain the durability of fan motor blades. Apply lubricant to any metal material in your exhaust fan.

  1. Tighten the mounting screws

The easiest and cheapest way to fix your fan.

  1. Replace the motor

Old motors wear out in time. Similar to car engines, when they are old, they need to be replaced after several years of running.

How Much Oil Should I Use on My Ceiling Fan?

You can only determine how much oil or lubricant you need for your fan if you open it.

The constant use of the exhaust fan will wear out sooner than expected and therefore requires cleaning, oil, and repairs.

If the machine starts to make noise, it may have consumed up the oil in its reservoir and hampered its operation. The unoiled appliance will not function properly if not taken care of.

Do the following when applying oil.

  • Turn off the power and unplug the machine from the electric outlet
  • Open the bathroom exhaust fan cover
  • Remove fan assemblies one by one. Don’t forcefully pry stuck parts.
  • Remove dust, dirt, and other debris
  • Inspect the bearing
  • Carefully apply oil
  • Do a spin test before putting the blade back to the shaft
  • Reassemble the fan

Can you use wd40 on a Bathroom fan?

Yes, you can! WD-40 lubricant effectively dissolves hardened grease, breaks them up, and leaves the metal part as good as new.

Drip the fan by spinning it to remove excess oil and to ensure the parts are moving fine. Don’t use abrasive materials for wiping the oil, as they will damage the finish.

What is a Backdraft Damper for an Exhaust Fan?

Draft or draught is the sudden burst of wind. In essence, a backdraft damper is a piece of device attached to exhaust ducts to let air flow efficiently to the outside and prevent the unwanted airflow from going back inside.

Backdraft dampers efficiently seal backdrafts and do not cause noise.

A roof cap or roof vent has the same function; specifically called a soffit, it serves as a vent cover and prevents bad air from getting inside the roof underlayment or attic.

A vent hood or Broan, on the other hand, is for gas ranges.

Are Bathroom fans Supposed to be Noisy?

It is common for a bath fan to make sounds, such as a humming sound, when they are on, and this should be harmonious enough not to disrupt the bathroom user.

When a bathroom fan starts to make a noise, that’s a different story, and this guide on bathroom exhaust fans answers your question.

How do I get rid of extractor fan vibration noise?

Extractor fans can be replaced if you want, and if the noise becomes a nuisance, you can’t get the nasty vibration out of your head.

Hence, your exhaust fan must work effectively, warding off bad air and wind and then further damage from exposing the erratic fan.

How do I fix my squeaky bathroom fan?

First, identify what’s causing the squeak. Usually, metal parts grinding with each other are the ones that squeak when there is insufficient oil.

Apply lubricant to joints and other connecting parts like bearing, shaft, fan blade, screws, etc., and check if the application of oil reduces the squeaky sound.

What is an air handler, and what does it do?

An air handler is a unit in an HVAC system that regulates the circulating air inside the house or building.

An air handler is mistaken for a furnace as they are both parts of the HVAC system but differ in function.

For a more complex discussion on the HVAC system, heater or water heater, blower wheel in an AC, and many more are parts that can produce all kinds of noise.

What is the difference between an air fan and a blower?

Fans provide simple airflow, while blowers provide direct and strong airflow.

PRO TIP: Backdraft dampers can also be used on dry clothes, microwaves, and range exhaust hood vents aside from bathroom exhaust units.


Make your bathroom experience one of the most pleasurable moments in life.

This guide should give you an idea of how you can maintain peace in your bathroom and prevent the weir knocking noise!

Anybody can get agitated when your bathroom exhaust fan suddenly makes those annoying sounds. But the best way to keep it from making noise further is to check the source of the noise and do a routine checkup on every electrical appliance you have at home.

Periodic maintenance with your bathroom exhaust fan will save you a peaceful day and money and time thinking of non-sensible solutions when you have no idea of the actual cause.

Get rid of your obnoxious old exhaust fan and replace it with a brand-new unit that runs seamlessly and is quieter than you expect.

Robert Castelao
Robert Castelao

Robert is an electronic engineer with more than five years of experience with a solid affinity for helping people reduce noise. He writes about these silent home appliances and easy soundproofing measures to help everyone avoid the negative effect of extended exposure to high noise levels.

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