Know Your Sones Before Buying a Bathroom Fan!

bathroom exhaust fan

Nothing can ruin a candlelit soak like the whirr of a loud bathroom fan. It can be grating. But a bathroom exhaust fan is critical to prevent bathroom mold, which is not only ugly but also a health hazard. So what’s the solution? Getting a bathroom exhaust fan with low sones.

The level of noise from a bathroom fan is measured in sones. This measurement increases linearly and is based on the human perception of noise. Therefore, 2.0 sones are twice as loud as 1.0 sones. Bathroom fans range from 0.3 sones to as high as 6.0 sones. For a quiet fan, look for a sone rating of less than 1.0.

When you buy a new fan for your bathroom, you’ll need to look at many factors, including the size of your bathroom. A bigger bathroom is going to need a better, bigger ventilation system. A higher ceiling will probably need extra ventilation. Unfortunately, many people forget to consider sone!

What Does the Sone Rating Mean for a Bathroom Fan?

A woman cleans the bathroom fan

When it comes to noise, the number you want to pay attention to is the sone rating. The sone rating will be a good indication of whether you’ll be happy with the noise level of the fan. Unfortunately, all sone ratings are meaningless if you have no idea what they mean.

What are sones? Sones is a relative measure of sound, unlike decibels. Decibels measure physical sound, but how we humans process noise also depends on the frequency (hertz level) of the sound.

If you were in a library whispering to a friend, that’s probably around 30 decibels. If you keep the decibel level the same but pitch the whisper higher, chances are you’ll disturb more people. Lower frequencies seem quieter to us than higher frequencies, even if they’re the same decibel rating.

This is where the sone system comes in, as it takes into account the human perception of how loud a noise is. A higher sone rating means a louder fan, and a lower sone rating indicates a quieter fan.

What Does a Quiet Bathroom Fan Sound Like?

A quiet bathroom fan, while it won’t be silent, will be pretty discreet. With modern bathroom fans, the technology has improved, so if you’re still sitting with a clunky old fan, you may be very pleasantly surprised. 

So, what’s the best sone rating for a quieter fan in your bathroom? As I’ve said, the lower, the better, but it will depend on your bathroom size. However, a quiet fan is between 0.3 sones and 1.0 sones.

A fan of 1.0 sones will be roughly comparable to the hum of a refrigerator. That’s pretty quiet and is usually low enough for most people. However, fans can be as quiet as 0.3 sones, though most commercial fans go up to about 0.5 sones.

A fan with a 0.3 sone rating will sound about as loud as the rustling of leaves. As you can imagine, this is very unobtrusive. If you are very sensitive to noise like me, spending more money on a fan with a very low Sone Rating is well worth it. 

The Winner of the Quietest Fan!

KAZE APPLIANCE bathroom fan on white background

For those on the lookout for the quietest fan, The KAZE APPLIANCE ultra-quiet bathroom exhaust fan is a winner at only 0.3 sones. This fan is designed for a bathroom ceiling fitting.

Because this is a larger unit, you may need to enlarge your existing fitting. The housing is made of galvanized steel painted to be rust-proof. This very quiet fan is suitable for a bathroom of up to 120 square feet. 

The Runner Up

Broan-NuTone AEN50 Invent ENERGY STAR Certified Single-Speed Ventilation Fan on white background

A good bet for small bathrooms under 45 square feet is the Broan-NuTone AEN50 which is whisper-quiet at 0.5 sones. This efficient fan comes from a well-known maker of reliable bathroom exhaust fans and is easy to install. It is an energy-efficient choice that will help control your bathroom humidity.

What Does a Fan With 2 Sones Sound Like?

Amazon Basics AB-BV101 Bathroom Fan  on white background

Some 2.0 sone fans are easily 10 times less than the price of a unit with a 0.3 sone rating. But what does this mean for sound level?

Well, you’ll know it’s running when it’s on. A fan that is rated 2.0 sones will sound like a loudly humming fridge – twice as loud as a 1.0 sone model. But on the plus side, you are unlikely to hear through a closed door.

If you have a bathroom of 70 square feet or less and are looking for a basic ceiling fan that is easy to install, then this two sones fan from Amazon Basics will do the trick. It’s an economical unit that includes all your required hardware and instructions, with a good installation video to guide you.

What Do 3 Sones Sound Like?

As for sone limits, 3 sones is about as loud as the average noise level of a busy office. And for me, that’s far too loud for a relaxing bath! Or even to run while I’m in another room nearby. 

With a fan with this kind of rating, it would be more useful for a commercial environment. A fan with 3 sones is definitely not relaxing.

Some people have fans that are as loud as 4.0 sones. Imagine hearing the sound of your television through a closed door – that’s the kind of sound level you could expect. If your bathroom fan makes this level of noise (and some do!), then it’s definitely time to upgrade. 

Best Bathroom Fans With Different Sone Ratings

FanSone RatingSounds LikeCFM
Kaze Appliance
Ultra Quiet Bathroom
0.3Rustling Leaves120
Broan Nu-tone
1.0Hum of a Quiet Fridge110
Amazon Basics
2.0Hum of a Loud Fridge70
Broan Nu-Tone A1103.0Office Noise110

What Else Affects the Noise Level of a Bathroom Fan?

There’s a balance between affordability and sound. A few things will also affect the sound level, such as the size of the bathroom vent:

  • Bigger venting equals a quieter fan
  • Screw fittings are quieter than nails
  • Angles in venting increase noise

What Is The Difference Between CFM And Sones?

When you’re shopping for your fan, you may be a bit overwhelmed when it comes to CFM. As you now understand, the sone rating will let you know how loud the fan will be, but CFM is still important to get right, too; otherwise, your fan may not be efficient at reducing mildew and humidity.

CFM is the abbreviation of Cubic Foot Per Minute. CFM gives you an idea of the rate of airflow that passes through your fan. A larger bathroom will require a higher CFM rating

A rough guide is that your CFM should, at minimum, equal the square footage of your bathroom. You can get a good estimate of this by measuring the length and breadth of your bathroom and multiplying the figures. 

For example, a bathroom that is 9 feet on the long wall and 7 feet on the short will give you a bathroom of 63 square feet. You would not want to put in a bathroom exhaust fan with a CFM rating lower than 63.

Special Consideration for Very Large Bathrooms

BV Bathroom Fan Ultra-Quiet 200 CFM on white background

If your bathroom has a very high ceiling, you may need an even higher CFM rating than you’d get multiplying length time width, as there is more vertical space.

A bigger bathroom will require a stronger fan. And this means a higher CFM rating. A higher CFM will usually means a higher sone rating

With bathrooms over 100 square feet, it’s best to include an additional 50 CFM after you calculate the square footage.

For example, if you have a 150 square foot bathroom, you would not want to go below 200 CFM. A suitable fan with a low sone rating of 2.0 would be the BV Ultra-Quiet, designed for bathrooms of up to 150 square feet while still being as quiet as possible.

More expensive fans will run higher CFM rates while still keeping to low sone rates, but don’t try to budget by dropping to a CFM rating that is too low just to get a low sone. You’ll end up with a fan that is ineffective for your bathroom, leading to high humidity levels and possible future mold and mildew damage.

See it on Amazon

Other Considerations for Buying a Bathroom Fan

In addition to the Sone Rating and the CFM, you’ll want to consider these factors when buying a bathroom fan:

  • Price
  • Where you’d like to install the fan (ceiling, wall)
  • Ease of installation
  • Optional extras like built-in lighting, Bluetooth, heaters
  • Where the moist air is going to be vented
  • The energy efficiency of the fan

And see this post for more ideas about how to make your bathroom more energy-efficient.

 Smart Bathroom Fans

If you’re dedicated to energy efficiency and saving money in the long-run, you might want to consider a smart fan. These fans have built in humidity-sensors so they will automatically turn on when the bathroom humidity exceeds a percentage that you set. This can help save money in the long run by preventing an expensive-to-remediate mold problem down the road.

Many smart fans also have motion sensors. You can set these to automatically shut off a certain number of minutes after someone leaves the bathroom. This can be quite energy efficient, especially if you’ve got little ones and teens who might not be turning the fan on and off when you’d like.

Other smart fan features for a bathroom can include dimmable LED lighting and a built-in Bluetooth speaker. Read my post on How Smart Bathroom Fans Work and Top Picks.

Fan Noise and Safety

what are sones for bathroom fan

A noisy fan can be a warning. If your fan is starting to make more noise than it should, this is a sign it’s time to have a look at what might be causing the problem. A fan in the bathroom is, after all, an electrical appliance. And household electrical appliances can be a major fire risk if they are not maintained to safety standards.

If your fan is looking a little worse for wear, making strange noises, or is slow to start up after you switch it on, you could be looking at a fire hazard.

Especially in older houses, you may have no idea how long that fan has been in use. If you’re in any doubt, it’s time to retire that scraping racket and potential safety hazard and get yourself a new fan installed.

Several maintenance tips will help keep your new fan safer for longer:

  • Keep the vent free from dust and dirt build-up
  • Remove the faceplate to clean it in soapy water
  • With the faceplate removed, wipe down the fan interior
  • Use a duct cleaning extension kit to keep dust from building in the exterior ducts
  • Switch the fan off when the bathroom is not in use

Troubleshooting A Noisy Bathroom Fan

cleaning the bathroom fan reduces noise

If you have a loud fan in your bathroom that is far too loud for its Sone Rating, but it’s still in excellent working order, you may be able to troubleshoot with these simple tips:

  • Safety first! Always ensure that you have switched off all power to the bathroom before working on the fan. Remove the fan cover vent and all the housing
  • Using a rag and a mild solution of soap and water, clean the fan, and motor assembly housing
  • If any parts appear damaged, rather replace the fan
  • Replace the duct with a larger size. A 6″ duct is one of the best choices for reducing sound. If this seems like too big a job, call a professional
  • Tighten all mounting screw fittings. Loose screw fittings could buzz due to the vibration of the rotating fan
  • If the fan is making a knocking sound, you will likely need to adjust the alignment of the fan within the housing. The sooner you can do this, the better, as this will damage your fan, and you may have to replace it
  • Apply a lubricant like WD-40 to the shaft of the fan after you have cleaned it

If these fixes don’t help reduce noise or you discover that your bath fan is damaged, you will have to replace the old fan. Replacing your fan doesn’t have to be a frightening task. Modern bathroom exhaust fans are made to be simple and easy to install.

This useful video from Lowe’s Home Improvement walks you step by step through how to replace and install a fan in your bathroom.

Know the Sone Rating to Get the Right Bathroom Fan

When it’s time to buy a new bathroom exhaust fan, measure the square footage of your bathroom. This will ensure you choose the correct size fan for your space. Using the CFM and Sone Rating as guides, you will now be able to navigate buying the quietest fan for your bathroom. 

Remember that a higher CFM rating will move air through a larger space, and a lower sone rating will be quieter. With these numbers in mind, you should be able to budget for a bathroom exhaust fan that dehumidifies the bathroom and is quiet enough to help you relax in the bath. (Here are 21 Relaxing Bath Ideas to help you find your bliss.)

But sometimes the noise in your bathroom doesn’t come from the fan. Here are some tips to reduce the noise when filling your tub

And sometimes you have noisy roommates or family members lurking nearby while you’re trying to soak in bliss.

In this case, go for a bathroom audio solution so that you can listen to some tunes rather than the chatter of your neighbors.

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