Imagine this: you have just arrived home after a long day and sit down to enjoy some peace and quiet. But then it begins—a constant hum that seems to grow louder. Your ventilation system sounds like it’s trying to communicate something. It’s not quite a highway, but it’s loud enough to start getting on your nerves. The more you try to ignore it, the worse it feels. If this sounds familiar, you’re not alone. Noise can be a sneaky problem that affects quality of life, and if you’re not aware of what noise management means, you may end up living with this issue unnecessarily.
In this article, we dive deep into why ventilation systems make noise and how we can control this noise by carefully calculating and planning the ventilation correctly. We will go through what it means to understand the mathematics of sound levels and how you can apply this knowledge to solve noise problems with your home ventilation system.
Before we dive deeper into solving noise issues in ventilation systems, it is important to understand the sound level regulations and acoustic standards that define what kind of sound environment is acceptable in different buildings. In Finland, these regulations and standards have significantly evolved over the past decades to meet improved quality requirements for both living and working environments. This development has been driven by a clear need to ensure that buildings provide a pleasant sound environment that supports a good quality of life and reduces health risks that excessive noise can cause.
The development of sound level regulations and acoustic standards in Finland
The original regulations primarily focused on sound insulation and noise control between buildings, but over the years, they have become more precise and expanded to cover noise management caused by ventilation and other HVAC systems (heating, water, ventilation, electricity). Along this journey, there have been many updates that have introduced even more specific guidelines and limits that guide today’s design and construction.
Let’s take a look at how these regulations and standards have evolved and how they affect the way ventilation systems are designed and implemented today.
The early stages of sound environment regulations: the first step
The drafting of regulations related to the sound environment began in Finland as early as 1948, but the first official steps were not taken until the 1970s. Before 1976, everything was largely the Wild West. Although there were preliminary proposals that laid the groundwork for the future, they did not yet lead to concrete changes. This all changed in 1976 when the first official sound insulation regulations were introduced as part of Section C of the Building Code Collection. This was a significant step forward. The regulations primarily focused on preventing unwanted sound from traveling between different spaces. This was the original purpose of sound insulation, and it laid the foundation for future updates and refinements.
D2 Regulations (1978): controlling the noise of supply air
The D2 (1978) regulations introduced a new dimension by focusing on noise caused by incoming air in buildings. Why? Because ventilation can easily ruin even the best acoustic design if its generated noise is not controlled. For the first time, these regulations provided guidelines on how ventilation systems should be designed and installed to avoid excessive noise. Noise control became an integral part of the design process, making it one of the cornerstones of ventilation system design and use.
C6 (1984) and C1 (1985) regulations: a deeper dive into acoustics
In 1984, the C6 regulations on HVAC equipment acoustics in residential buildings were published, followed closely by the C1 (1985) regulations in 1985, which marked a significant update. This time, the focus went deeper. The regulations presented the first clear reference values for sound levels in different spaces, such as residential rooms, patient rooms, and offices. This was the first time in Finland that A-weighted equivalent continuous sound levels (LA,eq,T) and maximum sound levels (LA,max) specifically for HVAC system noise were provided. The goal was to ensure that all sounds, including those from technical systems, remained within permissible limits.
D2 (1987) regulations: indoor climate and ventilation improvement
The 1987 D2 (1987) regulations provided clarifications regarding indoor climate and ventilation issues. The previous regulations on ventilation were updated, with a closer focus on how noise management of ventilation systems affects the indoor air quality and living comfort of buildings. These regulations were in effect until 2003 and laid the foundation for future development.
C1 (1998) update: noise control comes into the picture
The C1 (1998) regulations, published in 1998, expanded on previous regulations to include noise control within buildings. This was a significant development as it also considered external noise sources, such as traffic and other environmental noise, and their effects on the indoor environment of buildings.
SFS 5907 (2004) standard: the power of classification
The SFS 5907 standard, published in 2004, introduced the concept of acoustic classification. It divided buildings into four different acoustic classes, enabling more precise sound environment management for spaces intended for various purposes. From schools and hospitals to offices and industrial spaces, the standard provided clear guidelines and criteria for the quality of the sound environment.
YMa 796/2017 and the 2019 update: the sound environment in the modern era
The decree of the Ministry of the Environment (YMa 796/2017), published in 2017, regarding the sound environment of buildings, introduced modern requirements for sound insulation and noise control in buildings. This decree is still in force and covers both new construction and renovation projects. It sets clear requirements for the management of sound levels in HVAC systems, such as ventilation.
SFS 5907 (2022): update and future direction
The second edition of the SFS 5907 standard, published in 2022, brought significant changes and updated guidelines. The standard focused on new measurement methods and expanded to cover new types of buildings and uses. This updated standard provides clear guidelines for designers and developers on how to ensure good acoustic conditions and comfort in all types of buildings.
The development of sound level regulations and acoustic standards in Finland has been a long and eventful process, continually responding to new challenges and needs. The management of sound levels in HVAC systems, such as ventilation, is a key part of this development and has received special attention in both Ministry of the Environment decrees and SFS standards. These regulations and standards aim to ensure that buildings not only look good and operate efficiently but also feel and sound comfortable to live and work in. With these guidelines and regulations, Finland remains a leading country in acoustic design and construction.
Why does ventilation make noise? Understand the basics
The first step in managing noise problems when ventilation makes noise is to understand where these sounds come from. Often, noise is caused by several factors: design and installation errors, improperly sized equipment, or lack of maintenance. Let’s go through the most common reasons why your ventilation system might be making noise.
Flow noise in ductwork: Changes in the direction or speed of airflow create flow noise in ducts. The most common places for this are bends, branch points in the ductwork, air leaks, and changes in the shape and size of the ducts. Imagine driving on a straight road—noise remains moderate. But if you start accelerating, braking, and constantly turning, the noise increases. The same applies to airflow: the more the air “turns” and “swirls,” the more noise is generated.
Noise from fans and other mechanical parts: The fans of a ventilation unit can generate vibration and structural noise, which is transmitted through the ducts into the room. If the fan is not balanced or the equipment is old and worn, the noise intensifies. This is noise that comes from the devices themselves and must be taken into account when designing effective noise attenuation.
Narrow-band noise: This is noise that occurs at a specific frequency and can be very disturbing because it may sound more “ringing” or resonant than a steady hum. This type of noise is particularly common in saunas or bathrooms, where the measured noise may be accentuated at a specific frequency, such as 100 Hz. This makes the noise subjectively more annoying.
Understand sound measurement: Sound power and sound pressure
If you want to control the noise of your ventilation system, you need to understand the basic concepts of sound measurement. This is where sound power level (LW) and sound pressure level (Lp) come into play. Both are important, but they are used in different ways.
Sound power level (LW) describes the power emitted by a sound source into its surroundings, and it is a physical property of the sound source. It is defined by the equation:
where:
W is the sound power of the sound source [W]
W_0 is the reference sound power (10^{-12} W)
This formula gives us a way to measure and compare the power levels of different sound sources. Sound power levels are often measured in acoustic laboratories because they provide the most accurate picture of how much noise a device actually produces.
Sound pressure level (Lp), on the other hand, measures how loud a sound is at a specific location, and it depends on both the power of the sound source and the environmental conditions (e.g., distance from the source, room acoustics). It is defined by the equation:
where:
p is the sound pressure [Pa]
p_0 is the reference sound pressure (2 × 10^{-5} Pa)
Sound pressure level is the loudness that we humans perceive. It varies depending on how far we are from the sound source and how much the sound reflects in the environment.
A-weighting: What really bothers you?
The perception of sound is not linear, which is why we need special filters for measuring sound. A-weighting (A-filter) is a filter that takes into account the sensitivity of the human ear to different frequencies. This is important because not all sounds bother us equally—low and high frequencies are perceived differently.
A-weighted sound power level (LWA) measures the annoyance of sound and is used in evaluating the noise of equipment, such as ventilation terminals. For example, the A-weighting for different frequencies is as follows:
Frequency (Hz) | 63 | 125 | 250 | 500 | 1000 | 2000 | 4000 | 8000 |
|---|---|---|---|---|---|---|---|---|
A-weighting (dB) | -26 | -16 | -9 | -3 | 0 | 1 | 1 | -1 |
With this information, we can more accurately assess how disturbing certain noise is at different frequencies and design noise attenuation specifically for those frequencies.
Adding sound levels: Understand logarithmic mathematics
Decibel values are logarithmic, so adding them together is not straightforward. When combining multiple sound sources and calculating their cumulative effect, the logarithmic addition formula is used:
This formula allows for a more accurate calculation of combining different sound sources and provides a realistic estimate of the noise level in a room or space.
Deeper insights into acoustics: octave band sound power level
To truly understand how sound is controlled, we need to examine the behavior of sound across different frequency bands. The octave band sound power level (LWokt) is an important concept when discussing sound management in spaces with multiple sound sources.
Octave band sound power levels are calculated using the formula:
where:
LpA10 is the A-weighted sound pressure level in a space with an absorption area of 10 m²-sab
K is the correction term specified for each frequency band.
This calculation model helps assess how sounds at different frequency bands behave and how they affect the overall noise level. It is particularly crucial in complex spaces, such as offices with multiple ventilation terminals, where this calculation can be essential for proper sound level management.
Controlling noise between rooms: How to manage sound transmission from one room to another
When discussing how noise travels from one room to another through ventilation ducts, it is important to understand that noise control is not just a one-trick solution. Many people think first of air ventilation silencers, and while they are often a great solution, they are not always the only or even the best option. Replace old air ventilation silencers with new ones if you have the chance, especially if they are filled with rock wool or fiberglass, which can dry out over time and release particles into the indoor air. Today, new air ventilation silencers are made from acoustic Dacron, which does not shed fibers and is a much healthier alternative. But don’t think that this is the only thing you can do.
Controlling noise between rooms requires a bit more consideration. Here are the key steps you need to take into account:
Choose the right terminal device (vent): When sound passes through a terminal device, it can either amplify or reduce noise. Therefore, choose a terminal device specifically designed to dampen sound. This small choice can make a big difference.
Use silencers effectively: Silencers are still one of the most effective ways to combat noise. If you have old air ventilation silencers, replace them with new, better sound-dampening models. And if you don’t have any, get them as soon as possible.
Select end-point terminal devices: Noise reduction does not stop at the first vent. The final terminal device, the one in the room, can also impact the noise level. Choose a terminal device that is specifically designed for noise control.
In addition, you can use so-called adjustment attenuators, which can be found in the selections of Inno and Jeven, for example. These foam pieces installed in the duct can be very effective, but you need to know how to use them correctly: open the vent or diffuser to the largest opening possible and let the adjustment attenuators do most of the work. However, keep in mind that these foam pieces collect dirt and dust over time, so they need to be cleaned regularly. And when you order duct cleaning, always remind the cleaning company about these devices so that they don’t accidentally remove them or put them back carelessly.
The result? Acoustic management is not just one solution but a combination of different methods and the right decisions that, together, ensure noise doesn’t rob you of sleep or peace at work. And when you get these things right, you create a space where peace prevails—exactly as it should be.
Practical tips for noise control in air ventilation systems
Now that we know where the noise comes from and how it is measured, let’s look at practical solutions for reducing noise:
Installing and upgrading air ventilation silencers: Sound attenuators are one of the most effective ways to control noise in ventilation systems. By choosing the right silencer that is optimized for a specific frequency range, you can significantly reduce noise. For example, if the biggest problem is in the 125 Hz frequency range, select an air ventilation silencer designed to work effectively at that range. Also, note that silencers should be installed as close as possible to the noise source (such as fans) and at critical points in the ductwork where airflow changes significantly.
Vibration dampening: Vibration is often the single biggest cause of noise in ventilation systems. Using vibration dampeners when mounting fans and motors prevents vibrations from transferring into the ductwork and then into the rooms. Also, use flexible duct structures or connections that can further reduce the impact of vibrations.
Redesigning ductwork: Design the ductwork as straight as possible and avoid unnecessary bends and constrictions. If the ductwork is full of bends, the airflow has to work much harder, which increases noise. Proper sizing of the ducts is also important: ducts that are too small result in higher airspeeds, which increase flow noise.
Room acoustic dampening: Sound does not only travel through the ventilation system—it also reflects off the surfaces of the room. Absorptive materials on walls and ceilings can help reduce the spread of sound from one room to another. When walls and ceilings are equipped with sound-absorbing materials, the noise level can be significantly reduced.
Checking and adjusting airflow rates and pressure differences: Noise levels in a ventilation system are also greatly affected by how well the airflow is adjusted. Excessive airflow rates or pressure differences can cause unnecessary noise and vibration. It is important to ensure that all ventilation devices and vents are functioning as planned and that airflow rates are balanced.
Active noise control (anti-noise technology): This method uses targeted noise reduction technology that produces opposing sound waves to cancel out the original noise. It is particularly effective at low frequencies, where traditional air ventilation silencers are not as effective.
Using simulation software: Use advanced simulation software that takes acoustic calculation models (such as sound pressure level LpA and sound power level LWA) into account. With these programs, you can simulate and optimize the sound levels of the ventilation system before actual installation. This allows for precise predictions of sound pressure levels in different rooms and enables you to design the system in advance to minimize noise problems.
Final thought: Noise control is an investment in a better quality of life
If you have ever had to live with constant noise, you know how quickly it can wear down both mental health and physical well-being. Noise affects sleep, concentration, and overall mood. This is why noise control is so important. It’s not just a technical issue—it’s about improving quality of life.
A well-designed ventilation system that takes into account sound attenuation, vibration control, and acoustics can work wonders for the comfort of a living space or work environment. When you know what tools you have at your disposal—sound attenuators, vibration dampeners, simulation software, and the right materials—you have the opportunity to create a space where you can truly focus and enjoy your life without distractions.
Remember, the best time to start managing noise was yesterday—the next best time is today. Don’t settle for a noisy home or office. Act now, use this knowledge, and make your spaces places where peace and quiet are more the rule than the exception.
This article not only gives you the basics and calculations for sound management but also helps you understand why it’s important and how it impacts your everyday life. Use this knowledge and start taking action today. It’s time to make your home and workplace as quiet and comfortable as possible.
Contact us today and ensure your ventilation is in order and as quiet as possible. We understand that noise problems can directly affect your quality of life—and we are here to make sure that doesn’t happen. While others take care of their parts, we focus on what we know best—ventilation. Our passion is to make your home and work environment quiet and comfortable places where you can focus on what matters and enjoy your life without disturbances. Don’t settle for a noisy solution. Take a step toward a quieter future and let us help you achieve it. Together, we can create a space where every breath is fresh and quiet.
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IVAeris Oy
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