All soft things absorb sound, right? Let’s see just how effective carpet is at absorbing sound.
Carpets typically absorb airborne noise by up to 35%. This number can double with specific materials and set-ups, with airborne noise reduction peaking at 70%.
This doubling is because the individual fibers of the carpets, their underlays, and piles tufts have different resonant frequencies at which they absorb sound.
In the rest of this article, I’ll explore how sound is absorbed, why exactly does a carpet absorbs sound, and why putting carpets in a recording studio may not be the best idea.
How Does Sound Absorption Work? Does Carpet Absorb Sound?
Defined as “the measure of the amount of energy reduced from a sound wave as it passes through a material,” sound absorption is a critical component in soundproofing, especially in places where acoustics matter a lot.
Reducing the amount of reflected sound through absorption helps reduce noise, echo and even improve the acoustic quality of a room or a building.
Many things absorb sound. A good example is whenever sound uses water as its medium (or as it tries to travel through water), it gets caught up within the molecules of the medium, in this case, the water.
When this happens, the medium turns the acoustic energy of the sound wave into heat, which in turn makes the molecules do something: vibrate.
If the same thing were to happen in this instance, a brick wall, something weird happens.
Unlike water and air, a brick wall is much denser, which means that sound will not make the brick wall vibrate at the same rate as the water in the example above. So instead, it reflects sound.
For a better acoustic experience, we want to have items that absorb sound rather than reflect sound. The good news is that sound is absorbed pretty well with carpets.
The Carpet and Sound Conundrum
If there’s one thing all of us can agree about, it’s that carpets are incredibly fibrous. The carpet is soft to step on by nature, but it also makes a good sound absorber.
Carpets absorb sound because within their fibers and their clusters, trapped air pockets occur that prohibit them from vibrating.
Unlike hard floors and walls, carpets and their complex structures and soft materials have different resonant frequencies.
This statement means that the different lengths of fibers, the varying materials, their scrimp, and spiralities each absorb a range of sounds. Which in turn signifies that they can absorb sound from an extensive degree of frequencies, from the lowest to the highest.
Different types of carpet material and construction can also affect how carpet absorbs sound.
For example, if the carpet fibers are too clustered or too impenetrable, sound may be reflected more, thus reducing sound absorption.
It is also important to note that wool carpets absorb many sounds, especially if the underlays are wood.
Humans do produce not only verbal noise but also surface noise. Surface noise includes noise created through friction and impact and can be pretty annoying, especially on houses with multiple residents or pets.
The good thing, though, is that carpets reduce airborne verbal noise and reduce surface noise.
Unlike the hard surfaces of tile floors, carpets have a soft texture that dampens the sound of friction of shoes, slippers, and other footwear. It can also dampen the sound of falling things.
Studies have shown that tile floors produce 7 to 12 times more sound in comparison to carpets.
Buying The Right Carpet for Sound Absorption
There are many variables to consider when buying the right carpet for sound absorption. For this article, let us look at three of these variables.
Surface construction refers to the surface of the carpet, whether the fibers are clustered or far apart. Surface construction also refers to the surface and its penetrability.
Additionally, whenever the fibers of the carpet are clustered together or have increased penetrability, the possibility of sound reflecting increases.
As the carpet’s surface emulates hard surfaces more and more, the amount of absorbed sound reduces. This property is why it is essential to buy a carpet with a pretty ruffled surface and has a pretty soft surface.
Carpet material is very significant when considering which carpet to buy. Some experts have vocally announced that wool is the most optimal material to be used whenever there is a consideration for sound absorption.
Experts have reasoned that this is because wool has the best sound transmission class and impacts transmission class compared to other materials.
Wool carpets have a dense amount of fibers while staying penetrable, implying that wool carpets can absorb more sound per square inch.
In addition to that, wool carpets’ fibers also have a tremendous variation in diameter, crimping, shape, and length. This variation directly contributes to the expanse of the sound frequency that the carpet will absorb. (4)
Not only does the carpet material matter, but it also does the carpet underlay. The carpet underlay provides a significant degree of sound absorption.
The most optimal carpet underlay for sound absorption are high-performance felt underlays which will cushion floors and reduce noise. Additionally, the felt is also a fibrous material that further enhances sound dispersion.
However, if one will use a heavy and dense underlay like vinyl, the sound absorption will be heavily hampered, as hard, heavy and dense materials stops a lot of sound vibrations.
Carpets and Acoustics
Studios, especially recording studios, are heavily intricate rooms with thoroughly researched materials. Each sheet, layer, wall, window, and even floor material has had thorough contemplation from the engineers.
With the sound absorption qualities, one may consider putting carpet in their studios to reduce echo. However, many sound engineers and experts do not recommend using carpets for professional settings.
Carpets are known to be absorbers of mid and high-frequency sounds, those you’d find on houses. Dog barks, human speech, and audio coming from the television are examples of these.
One might think that since carpets absorb mid to high-frequency sounds, it might work in their favor to put them into studios.
However, studios are incredibly delicate areas, and the bass that the carpet has not absorbed may heavily hamper the acoustic experience of an artist.
The cause of this effect is that the reflected bass results from the carpet’s thinness and structure. Studios with carpets will experience acoustics with a strange, low-pass filter and will have a “booming” quality.
So if this is the case, what exactly is the appropriate flooring material for floors? Oddly, the most appropriate flooring for studios is just a bare concrete floor, unpainted. Not very beautiful.
This part is where most of the people get confused. Hard surfaces were supposed to be the antagonist when it comes to acoustics. What happened to that?
Yes, even though hard surfaces are the enemy of acoustics, a hard floor is better to balance out the room. So a treated wall and window will balance this out with the untreated floor to have a more natural sound, especially when compared to either an utterly untreated room or a dead room (fully treated room).
The reasoning behind this is because our Brain trained our ears to associate echoes with nature, and so, a little bit of echo from the hard floor will be enough.
Frequently Asked Questions About Sound and Carpets
Are there better choices for sound absorption when it comes to carpets?
Acoustic carpets are carpets made exclusively to be excellent acoustically. Acoustic carpets are known to block out and absorb sounds effectively while staying stylish and premium-looking.
Where are the optimal places to put carpets for sound absorption?
There are many places where one may want sound absorption and good acoustics. It has been shown in many studies that good sound absorption in work environments helps boost productivity and reduce workplace stress.
Aside from carpets, what are good household furniture or items for sound absorption?
Recommended are foam tiles, bookshelves, weather stripping, and more items for sound absorption.
Bookshelves, in particular, specifically those floor-to-ceiling bookshelves, are fantastic at absorbing sound. Since bookshelves have a ton of mass, they also absorb many sounds, thus creating a much quieter environment.