Noise Absorption vs Sound Insulation

When most people think about the control of sound in an internal environment, their minds may conjure up images of the foam wall panels found in many recording studios. They’re a familiar image – often they look like rows upon rows of pyramid-shaped foam, or elongated foam prisms. When asked what they do, some might assume that they’re to insulate the room from external noise, others might say they’re to balance the sound within the room.

The truth is, not only recording studios, but offices, public venues, gyms and more require products and materials that perform both of these functions. Which of these two functions are foam panels used for? Why, and what else can be used? The answer to this question lies in the difference between noise reduction and sound insulation. To understand the former, it’s first important to understand reverberation. To understand the latter, we must understand noise transfer.

Reverberation

One might remember in their high school physics classes being shown how sound moves in waves. From its original source, it travels outwards like ripples on pond after a pebble has been thrown in. When these waves hit certain surfaces and objects, they’re partly absorbed and partly reflected, just as the ripples on the pond are, when they hit rocks, floating objects, or an edge.

In internal environments this allows sound to repeat, and often travel further than it would outdoors. Take an office, for example. If one person were to be speaking at one end, the sound of their voice will not only carry directly to another person, but will also travel to the ceilings and walls. The ceilings and walls will then reflect this sound back into the room. The effect is that a person on the other side of the office will hear not only the original sound, directly from the person speaking, but also the reflected sound.

Reverberation refers to the amount of time it takes for all that sound to die down; for the waves to lose momentum and stop reflecting. When there is an entire office of people making noise – talking, printing, eating, opening and closing doors – high levels of reverberation can make for an acoustically uncomfortable environment.

Not only does it rid people of their basic need for peace and quiet, but it can also drastically reduce much-needed privacy. In open offices or cafes, for example, conversations that require some degree of confidentiality are often held in places that aren’t separated by walls.

Noise absorption

Noise absorption aims to reduce the level of reverberation in a given environment, thereby ameliorating these issues. Certain surfaces and materials reflect sound more than others. The foam-pyramid panels found in many recording studios, and many other acoustic control products, are designed to absorb sound instead of reflecting it, thereby reducing reverberation.

But the goal here is the balanced absorption of sound, not its total elimination. A room where too little reverberation takes place feels acoustically ‘dead,’ which can be just as uncomfortable as a noisy environment.

 In 2013 a US company, Orfield Laboratories, demonstrated this by constructing the ‘quietest room on earth’, where sound is so effectively absorbed that it becomes unbearable. The longest anyone has been able to stay in the room, to date, is two hours.

Noise transfer

If noise reduction is designed to the control effects of reverberation within a space, what about sound that comes from external sources? This sound is encountered as a result of noise transfer.

Noise can travel through buildings in a number of ways; it can go through walls, ceilings and floors, it can go through HVAC systems, ducts and pipes, and it can go through breaches in the enclosure of a room, such as gaps in joints, sockets, and badly sealed doors and windows.

We’ve all been in scenarios where we can hear the plumbing from another room, the sound of footsteps from the floor above, or music from an unknown source. Noise reduction, within a room, will do little to have an effect on these sounds. Instead, what’s needed, is sound insulation.

Sound insulation

Ideally, in the construction phase of a building or space, careful attention will be paid to how sound can be insulated between different areas. This is not a matter of reducing the reflection of sound through air, it’s a matter of reducing the degree to which sound can travel through physical materials.

In general, sound has a hard time traveling through dense, high-mass objects and materials, and a much easier time traveling through light materials. In the construction phase, acousticians can consult on which solutions should be used for walls and partitions, how to include sound-absorbing layers, and how to treat ducts and pipes.

Improving sound insulation

In existing buildings, it’s possible to retrofit areas to improve sound insulation. This means first assessing the existing structure, performing sound insulation tests, and creating a comfort target. Then, adjustments are made. This often involves replacing existing walls and partitions with more acoustically appropriate ones.

In cases where this either isn’t possible or entirely necessary, it may involve placing acoustic panels on top of existing structures, so as to seal the acoustic envelope.

Case

In Shanghai, ZENFEEL helped law firm Dawo retrofit their offices to improve sound insulation. Between meeting rooms, we replaced a moveable partition wall with an insulated wall to increase confidentiality.

We also placed custom-made sound absorbing panels to reduce noise, giving a more balanced acoustic environment. The result was a high level of insulation, 40db of insulation, from 22db.

ZENFEEL Other Related Noise Absorption Acoustic Products

Besides offering consultation on noise-reduction projects, ZENFEEL has an array of its own products that can help achieve acoustic comfort.

– ZENFEEL Smart-Panels. These acoustic panels are designed with two key layers – front and back. The back layer is where most of the noise absorption happens; it is made with our Eco Fiber sound-absorbing materials. The front layer is polyester, and is there to adapt to any number of aesthetics. It can be coloured, printed on, have carved styles and use 3D patterns.

– ZENFEEL ceiling products

o Suspended islands. These panels simply look like design features; the fact that they’re there for acoustic control would never cross most people’s minds.

o Baffles. These don’t only absorb sound, but also give ceilings an aesthetic, modern-feel.

o Flocking spray. This may be used to coat existing ceilings, such that they no longer bounce sound back down into the room.

– Standalone acoustic decorative items

o Menhir acoustic column. The sleek design of this column allows it to blend in, in virtually any workspace.

o Standing Partition. Traditional partitions bounce sound right back into an environment. The Zenfeel partition, while looking almost like a nice artwork, eliminates that problem.

o Carved suspension. The polyester fiber suspension allow for acoustic control, and a degree of privacy, while allowing light to still pass through.

Of course, the Zenfeel team will provide acoustic products and services that go way beyond these examples. Stay tuned to find out about more of our products.

For more information about creating acoustically comfortable work environments, or to see more samples of our work, reach out to ZENFEEL today.