What are Sones?

What is a Sone and How Can You Improve Yours?

By Pete Schrader
Associate Product Manager

Before I started working at Broan-NuTone®, exhaust ventilation crossed my mind exactly one time in 24 years. I was staying in a hotel, traveling for my previous job, and I went into the bathroom to take a shower. Much to my chagrin, as I flicked on the bathroom fan, there was no change in noise, no loud growl alerting me that the fan was working. I had been trained, subconsciously, that when you turned on the fan in a bathroom, it was supposed to sound like an airplane taking off, that’s how you knew it was working. I equated a higher noise level with better performance, ipso facto, no noise meant the fan didn’t work, right?
Fast forward a couple of years to my first day at Broan-NuTone®. One of the first things I learned was the quieter the fan, the better performing and more expensive it is. As I sat in that conference room, listening to my colleague tell me the intricacies of bathroom ventilation, my mind drifted back to that hotel fan two years ago. Was that fan actually a really high performing fan? Was I the only person who didn’t know that quieter was actually better when it came to exhaust ventilation?

While I can’t tell you definitively whether or not that hotel fan was high-performing or just broken, I do have a pretty good idea that I’m not the only person who didn’t fully understand sound as it related to bathroom ventilation. But, now that I have some product experience at Broan-NuTone, I feel like I’m uniquely qualified to explain sound and sones, so other people don’t struggle as I once did.
The first thing that you need to know is that sones are a measurement of sound, similar to decibels. The difference between sones and decibels is that sones are linear, meaning that 1.0 sone is exactly half as loud as 2.0 sones, and 2.0 sones is half as loud as 4.0 sones. Sones are typically measured in half-sone increments (1.5, 2.0, 2.5, etc.), but there are some cases as products get quieter, where sones will be listed in tenth-sone increments (0.6, 0.7, 0.8, 0.9, etc.)

The next thing to understand is what the different levels mean. Typical bath fans range anywhere from <0.3 sones to 6.0 sones. Below is a chart detailing what sound level you can expect out of a certain sone level:
  • <0.3 sones: This is the lowest possible sone rating for a ventilation fan. At <0.3 sones, you won’t even know the fan is running (maybe like my hotel experience?)
  • 0.3 – 0.9 sones: Fans in this range are also high-performing. It is usually very difficult to hear products in this range, unless you are specifically listening for them
  • 1.0 sone: A 1.0 sone rating is roughly equivalent to the sound of a refrigerator running
  • 2.0 sones: 2.0 sones is the noise level in a normal office workplace
  • 3.0 sones: A fan rated at 3.0 sones will be roughly as loud as a face-to-face conversation
  • 4.0 sones: This sone level is typically what people will listen to the TV in their home at
  • 5.0 sones: A 5.0 sone fan will be about as loud as a busy restaurant during dinner time
  • 6.0 sones: Fans at 6.0 sones are equal to the noise at a sporting event in an arena or stadium
The final thing you need to know is that there are ways to change a sone rating in your bathroom fan. The first one is obvious, buy a new bath fan! Broan-NuTone has a ton of easy-to-install ventilation fans that make it easy for DIY’ers or contractors to quickly retrofit their old, loud fan. We even offer selectable speed fans which have three different settings built right into the fan! The second way is to purchase a speed control switch. Broan-NuTone offers a speed control that connects to your bath fan and allows you to adjust your sound and CFM anywhere from 100% down to 20%. For example, if you have a 4.0 sone product today, and you install a speed control switch, you can infinitely adjust the sound level of your fan anywhere from 4.0 sones to 0.8 sones! (Side note, as your sound decreases with the speed control switch, your CFM will also decrease, which means that your fan won’t move as much air.)

So, how loud is your fan and are you really ok with that?

Photo by KAOTARU on Unsplash
Photo by Krys Amon on Unsplash
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