Bathroom Fan Sones – How Many Sones is a Quiet Fan

A quiet bathroom fan is 0.3 to 1.0 sones.

Quiet bathroom fans make as much noise as normal breathing or whispering from a few feet away.

What is a sone? A sone is a measurement of sound, similar to decibels.  They are linear in that 1 sone is twice as loud as .5 sones. And 2 sones are twice as loud as 1 sone, etc.

Sone to Decibel Calculator

Most of us are familiar with noise level measurements in decibels. But sones is used quite commonly for household items like bathroom ventilation fans, aka bathroom fans and bathroom exhaust fans.

First, you can convert your fan’s sones rating to decibels.

And then you can view the chart to compare your bathroom fan’s noise level to common activities.

Sone to Decibel Chart:

A fan with a noise level of 1.0 sones or less is extremely quiet. Manufacturers sometimes use the phrase “whisper quiet,” and in this noise range, it is certainly true.

1.5 sones is fairly quiet for a bathroom fan – it is a little higher than average for good-quality fans.

Once you get above 2.0 sones, like a bathroom fan with a noise level of 2.5 sones, the sound is noticeable and might be bothersome if your bathroom is all tile – a material that makes noise bounce around rather than damping it.

But let’s be honest – many homeowners want their fan to be a little louder to drown out bathroom noises, right? If your home is small and/or there is a bathroom close to the kitchen or living areas, a fan that runs at 2.5 sones or higher might be preferred. For example, many popular Broan-Nutone bathroom fans run at 3.0 sones by design.

And 3 sones is loud for a bathroom fan. It is about as loud as a face to face conversation using a normal indoor voice. As the sone to decibel calculator shows, 3 sones is 44 decibels. It is considered loud but not too loud for a powerful bathroom fan.

Quietest Bathroom Exhaust Fan for Different CFM

Why do you want a quiet bathroom exhaust fan? As noted above, some prefer to have a loud bathroom fan. 2.0 to 3.0 sones provides a fair amount of “white noise” that makes bathroom use more comfortable for some family and guests.

However, if your bathroom is near bedrooms with light sleepers that are easily woken up, then having the quietest bathroom exhaust fan might be preferred.

Here are common bathroom fan CFM ratings and the quietest fans in that range.

CFM – This is the cubic feet per minute the fan moves through it. The higher the CFM, the more powerful the fan.

This chart is based on 3000+ models of HVI certified bathroom exhaust fans. You can check the specific models with lowest sones here.

HVI is the Home Ventilation Institute, an industry organization that provides accurate and independent third-party testing for bathroom fans and other types of household fans. If you are concerned about the accuracy of the ratings given on the fans you are considering, be sure to choose an HVI-certified fan.

How to Make a Bathroom Fan Quieter

If you prefer to have a quiet bathroom fan, but yours is louder than you want, here are steps you can take to make a bathroom fan quieter.

A lot of these tips for making a bathroom fan quieter start with removing the cover. Here are the tips and the types of bathroom fan noises they solve.

1). Tighten any screws, nuts or bolts you can reach. Start with the mounting nut holding the blade to the motor assembly. Don’t over-tighten it, or you’ll risk cracking it. Just make sure it is snug plus about a ¼ turn. Tightening these items will limit vibration noises like rattling or knocking.

2). Apply thin foam to the bottom of the cover where it contacts the ceiling. Replace the cover. This will stop noisy vibrations too. A product called Sorbothane is a peel-and-stick 3M acoustic and vibration damping foam that is very useful for this purpose.

3). Clean away dirt and built-up debris from the fan motor, blades and cover. If the fan is making a high humming noise or grinding sounds, cleaning might reduce or eliminate the sounds.

4). Increase duct size. If you have access to the attic, locate the duct running from the exhaust fan to the exterior wall of the attic. Make sure it is the right size for the fan. If there’s a reducer on the fan, remove the reducer, and install the properly sized larger duct. This will reduce whooshing or hissing noises.

5). Check the housing around the fan. Is it crooked, allowing the fan blades to hit it? Straighten it and tighten it, if possible. This will stop knocking sounds.

6). Oil the fan motor and where the blade attaches. A drop or two of household oil like 3-in-One oil can do wonders for squeaky parts. White lithium grease is another useful product to quiet noisy bathroom fan squeaks and squawks.

7). Replace the fan motor. If you are sure it is the fan motor that’s making a racket, you’re handy and know how to safely work on electrical appliances – then consider fan motor replacement. Motor and blade assemblies are inexpensive – a lot less than replacing the entire unit.

8). Absorb the sound. Noise bounces around in a bathroom with all hard surfaces. Put down a large bath mat. Use a thick-fabric shower curtain. Use fabric hangings or sound-deadening panels on the wall or the back of the door.  

9). Replace the fan. If these tips for how to make a bathroom fan quieter don’t work, then replacing the bathroom fan might be your only option.

Keep in mind that today’s quietest bathroom fans run at less than 1.0 sones. They are more energy efficient than older units too.

Replacement tip: When quiet operation is your primary goal, buy a new bathroom fan that is the right size for your bathroom. One that is more powerful than necessary will make more noise too.

Small bathrooms – up to 45 square feet or about 9×5: 50 CFM is sufficient. Sones are 0.3 to 1.0.

Medium bathrooms – Up to 80 square feet or about 10×8: 80 CFM is enough, but 100 CFM fans probably won’t be too loud. This size is usually 0.5 to 1.5 sones depending on the model. 

Large bathrooms – Over 80 square feet: 100 CFM to 150 CFM fans are recommended. The noise level of these bathroom fans is 1.0 to 3.0 for most models. 

Written by Rene Langer

Rene has worked 10 years in the HVAC field and now is the Senior Comfort Specialist for PICKHVAC. He holds an HVAC associate degree and EPA & R-410A Certifications.