What Is a Sone and Why Is it Important?
Creating a comfortable living environment involves many different factors, but one that often sneaks up on us is the noise generated by a home’s HVAC systems, including heating and cooling units, kitchen exhaust fans, and bath fans. That noise is measured in “sones,” and it makes a big impact on both residential comfort and how much consumers use those appliances. It’s also subject to industry regulations.
Let’s explore the world of sones and why they matter.
Understanding Sones, Sone Ratings, and Their Significance
A sone is a unit used to measure the perceived loudness of sound and tells us how humans discern the intensity of noise. Sones are a bit different than other noise measurements like decibels (dB). Decibels measure the physical sound pressure level, while sones consider how humans hear and interpret sound. This difference matters because different frequencies and tones can affect how we perceive loudness, even if the sound pressure levels stay the same.
For reference, 1 sone is about the same as a running refrigerator. A quiet office rings in at 2 sones. A television at a normal volume is 3 sones, and 4 sones is equivalent to a two-person conversation. Eating out at your favorite restaurant is about 6 sones, light to average traffic is 7 to 8 sones, and nine to ten sones is equivalent to congested traffic.
When it comes to fresh air appliances and exhaust fans, sone ratings help us gauge the overall acoustic comfort within a space. Different areas in a home, as well as the purpose of the item creating the noise, decide what’s an acceptable sone level.
For instance, lower sone ratings are desirable in spaces where people spend a lot of time, like bedrooms or living rooms. When it comes to bath fans, a recommended maximum sone level is usually around 2 sones – that’s the level at which a fan can still qualify to be ENERGY STAR® approved. On the other hand, kitchen fans can have a slightly higher level, due to their specific usage; so, their recommended sone level is 6-7, which is about 600 cfm.
Factors that Contribute to and Attenuate HVAC System Noise
Several factors can influence a fan’s noise levels and increases it’s sone ratings, including:
- Motor type
- Speed of the moving parts
- Ductwork and the layout of the ductwork
- Level of restriction
- Overall design
Poorly designed or maintained equipment, insufficient sound insulation, and excessive vibration also can contribute to an increase in sones.
Sound Attenuation and Minimizing Sones
Sound attenuation is the process of reducing or minimizing sound transmission. When we relate it to HVAC systems, it involves various strategies a system designer can use that help to reduce noise.
- Sound-insulated ductwork – This type of ductwork is designed with special materials that absorb or block sound waves, reducing what can travel through the system and create unwanted noise. By using this type of ductwork, we can maintain a quieter and more peaceful indoor environment.
- Vibration isolation mounts – Ventilation fans and compressors tend to produce vibrations when running, and those vibrations can make their way into the building’s structure and result in irritating noise. Vibration isolation mounts help solve this problem. These mounts are specially designed to dampen vibrations, keeping them from transferring to the building structure. By isolating the equipment, the mounts help ensure a quieter atmosphere.
- Acoustically designed equipment enclosures – These enclosures are crafted using materials that excel at absorbing sound. They trap and dissipate annoying sound waves, preventing them from escaping and causing disturbance in the surrounding space. By housing the equipment within these enclosures, we can contain the noise and significantly reduce the overall sound levels.
By combining these sound attenuation strategies, we can create a more peaceful environment as the measures work together to address the root causes of the noise and reduce sound levels throughout the space.
It’s also worth noting that a variety of factors come into play, including the specific HVAC system, the home or building’s layout, budget, and the noise reduction goals. Sound attenuation strategies should be addressed during the design and installation processes, as well as through ongoing maintenance of an HVAC system to ensure occupants can enjoy a more comfortable indoor environment, free from the disruptions caused by excessive noise.
Industry Regulations and Standards
Industry regulations and standards play a crucial role in ensuring acceptable noise levels in HVAC systems.
- Air Movement and Control Association (AMCA) – The AMCA publishes standards related to sound and fan performance for commercial and industrial use. They establish sone values at a distance of 5 feet from a hemispherical free field and calculate sones based on sound pressure of the eight octave bands. The AMCA requirements for fan sound performance is quite lengthy and can be found here.
- Home Ventilating Institute (HVI) – HVI establishes sone values at a distance of 5 feet from a spherical free field and calculates sones based on sound pressure of the 1/3-octave band values. HVI recommends that a quiet bathroom fan be no more than 1.0 sone and equipment be HVI certified for peaceful living.
- Environmental Protection Agency (EPA) - Some countries have specific regulations on noise levels and sones, and in the United States, that’s the EPA. They’ve established noise control regulations under the Clean Air Act, which addresses noise emissions from various sources, including HVAC systems.
- Local building codes – Local building codes often include guidelines for acceptable noise levels. Since the codes vary by region, it’s important to research specific regulations in your area.
Staying informed about industry regulations and standards can empower homeowners to make educated decisions for their own HVAC systems. And by opting for products that follow these acceptable noise level standards, everyone involved can be confident in a quiet system that still performs as desired.
Advice for Building Professionals on Choosing Quiet Ventilation Fans
As you embark on projects involving ventilation upgrades or installations in new homes, it is crucial to consider the noise level of equipment. Here are some essential factors to bear in mind:
- Conduct thorough research – Each building you work on is unique, and its requirements may differ from those of neighboring structures, even if they share the same layout. Consider the size of the space from which you work on. Larger areas can tolerate higher sound levels without appearing too noisy, but be mindful of potential echoes. It's generally a good rule of thumb to choose a fan that delivers the same cfm as the room's square footage. This approach ensures the fan can efficiently do its job without straining, leading to an acceptable noise level.
- Prioritize proper installation and maintenance – Ensure that the HVAC system is installed correctly, adhering to the manufacturer's guidelines. Regular maintenance and inspections are essential to keep noise levels to a minimum.
- Seek guidance from HVAC experts – As building professionals, you understand the value of expert advice. Consult with HVAC specialists who can help you through the selection process and recommend systems that prioritize noise reduction while maintaining optimal performance.
Nurturing Noise-Free Living with Acceptable Sone Ratings
Understanding sones and their significance in HVAC systems is critical for homeowners and building occupants. By considering sone ratings, implementing sound attenuation techniques, and following industry regulations, you can create a more comfortable and peaceful environment.
Looking to learn more about how Fantech products can help contribute to a quieter home or building? Check out our bathroom solutions or kitchen systems.
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