Sones Rating – What it is, What Affects it & More

Updated October 17, 2023

Industrial Fans Direct provides ventilation and heating solutions to thousands of businesses within the US and around the world. With over 20 years of experience, we’ve become the go-to provider for quality air movement and work environment solutions.

We know how frustrating disruptive noise from your industrial fans can be, which is why we’ve written this article – to help you understand what sones rating is, what factors affect it, and why it matters.

After reading, you’ll be able to determine what a “good” sones rating is and be better equipped to choose or adjust industrial fans for optimal, quiet performance.

Let’s dive in.

What is a Sone?

A sone is a unit of perceived loudness, helping gauge how people experience the intensity of sound from various sources.

The sones rating scale is very straightforward – 2 sones sound twice as loud as 1 sone. This system helps us compare different sound levels between sound-critical fans such as bathroom exhaust fans, circulation fans, inline-duct fans and wall exhaust fans.

These ratings are sometimes included within the technical specifications of a fan, allowing you to compare sones ratings across different products. However, if you don’t understand the level of noise to expect at each number, knowing an appliance’s rating will be useless.

What is a Good Sones Rating?

The answer to this depends on what you're looking for in your fan, and what setting the fan will be used in.

Generally speaking, a good sones rating for a quiet residential setting is below 2. A good sone rating for a large fan in an industrial setting can be anywhere from 4-10 depending on the size of the fan and installation location within you facility. 

If the fan is closer to an area where there will be people present, a lower sone rating is desired.  If the fan will be installed further away, then a higher rating is acceptable.

The quietest ones are rated at less than one sone, which is like a whisper. There are also several models rated between 1.5 – 2 sones, or just a bit quieter than soft music. These are good sone ratings for residential bathroom fans.

For reference, here are what different sones ratings generally sound like:

However, it’s important to note that sones rating or noise level doesn’t have to be a determining factor for what fan you decide to use. You may prioritize the volume of air it can exchange or you might be placing it in an environment that already has a lot of noise.

If that’s the case, then a “good” sones rating for you may be higher than it would be for someone who’s installing a fan in a residential building and prioritizes low noise level.

What’s the Difference Between a Sone and a Decibel?

The difference between a sone and a decibel is that a sone measures perceived loudness to the human ear, while a decibel quantifies sound intensity or pressure levels, making them different units for evaluating sound.

One of the most important differences is the way the sone scale is set up. It’s a very simple system, where the number serves as a straightforward multiplier. 

For example, three sones is three times louder than one sone. This makes it easier to imagine a certain sone level just by seeing the number listed.

Decibels, on the other hand, are calculated according to a formula that’s more complex. 

While a sound 10 times more powerful than near-silence is 10dB, one that's 100 times more powerful is only 20 dB. Meanwhile, a sound that's 1,000 times more powerful than near-silence is 30 dB. This measurement method often makes it harder to imagine how loud a certain dB level will be.

Click here to see our full Sone to dB conversion chart

Factors That Affect Sones Rating

A fan’s sones rating can be affected by a multitude of factors like fan speed, design, ductwork, and distance.

For instance, a faster fan speed or intricate design can lead to a higher sones rating and louder noise output. On the flip side, streamlined ductwork can contribute to a lower duct rating and less noise. 

Understanding these factors is crucial for selecting appliances that maintain a comfortable and quiet environment.

Fan Speed

A fan's speed directly influences its sones rating. You’ve probably noticed this before in your own home. You turn the fan speed to high, it makes more noise (high sones rating). You turn it to low speed and it becomes quiet (low sones rating).

Fan Design

A fan's design, especially the fan blade, also impacts its sones rating. A fan blade that’s aerodynamic, smooth, made from lightweight material, and has precise angling will ensure efficient air movement with minimal noise, yielding a low sones rating.

In contrast, a fan blade that’s heavy, non-aerodynamic, or has rough surfaces can cause disruptive noise levels, indicating a higher sones rating, despite the fan's speed.

Ductwork

Ductwork affects the sones rating by either amplifying or dampening sound. Inefficient, irregular, or constricted ductwork can cause air turbulence and noise, increasing the sones' rating. Properly designed and installed ductwork ensures smooth airflow, minimizing noise and contributing to a lower, more desirable sones rating.

Distance

Distance lowers the sones rating by reducing perceived loudness. The further you are from a noise source, like a fan, the quieter it seems. This distance makes the sound less bothersome and the sones rating lower, creating a more comfortable listening environment.

Are Sones Always Important When Choosing a Fan?

The decision to focus on sones rating when considering a fan will depend on your specific situation and needs. As we mentioned above, there are some scenarios where low noise is a necessity, while there are others where noise level isn’t as important.

For most residential uses, the sone level will be essential. Nobody wants to hear a roaring industrial noise throughout the house every time the bathroom fan goes on.

In commercial applications, however, there may be no need for a quiet fan beyond avoiding a deafening racket. Bathrooms in loud industrial installations are hardly going to be a source of disturbance if their fans aren't soft. 

Even when the surrounding area is quiet, many companies don't care much about bathroom fan noise as long as it’s in an area where customers can't hear it. Therefore, some commercial fan makers don't even list the sone levels of their fans.

Then there are commercial situations that are in a "crossover" situation. The bathroom may be used by customers, increasing the need for quiet operation, but the fan must also stand up to 12 or more hours of daily use. 

In this situation, a commercial fan is needed, but some attention should also be paid to its sound level. These fans are typically louder than the ones found in homes, but ideally, the sound won't be obnoxious either.

What Other Factors Should be Considered in Addition to Sones Rating?

While a residential fan's placement on the sone scale has a lot to do with satisfaction, it isn't the only factor to keep in mind. It's also important to pay attention to the CFM, or cubic feet per minute, that the fan can move. This tells whether the fan will be powerful enough for its intended placement.

To ensure that the bathroom fan is strong enough to do its job, look at the CFM rating first. Then, choose the one with the lowest sone rating for the quietest possible operation.

Check out our CFM Calculator here

Conclusion

In conclusion, understanding sones rating can be vital for choosing the right fan for your needs, ensuring a comfortable, quiet environment. 

We’ve delved into what a sone is, how it’s different from decibels, and the various factors like fan speed, design, and ductwork that affect it. Remember, a good sones rating is generally below 2, offering a noise level akin to a quiet office setting. 

At Industrial Fans Direct we’re ready to assist you in finding the perfect fan with an optimal sones rating, ensuring your utmost satisfaction and comfort. Contact us today to get started.

FAQs

What’s a good sone rating for a range hood?

A good sone rating for a range hood is generally below 2 sones. This ensures effective ventilation while maintaining a quiet kitchen environment, making cooking and socializing more enjoyable without disruptive noise.

What’s a good sone rating for a bathroom exhaust fan?

A good sone rating for a bathroom exhaust fan is below 1.5 sones. At this level, the fan works quietly and keeps your bathroom fresh and comfortable without an annoying sound in the background.

Can a low sones rating fan still be efficient in air circulation?

Yes, a fan with a low sones rating can still efficiently circulate air. The sones rating only measures the perceived loudness, not the fan’s ability to move air, which is indicated by its CFM (Cubic Feet per Minute) rating.

Are sones ratings available for all types of fans?

Unfortunately, sones ratings aren’t always available for all fan types – they’re primarily used for bathroom and kitchen exhaust fans. Industrial and ceiling fans might not provide sones ratings because they focus more on performance metrics like CFM and RPM.