Sound Diffuser Vs. Absorber – What’s the Difference?
Are you thinking about installing a sound diffuser or absorber in your studio or home entertainment area, but you have no clue which is which and if they are even different at all?
In fact, they are different, similar in ways because they are sued for acoustic treatment; however, different in their function and properties. Let’s take a look.
Sound Diffuser Vs. Absorber
A sound diffuser disperses the reflected sound waves away from the listening position while an absorber dissipates or absorbs it. As a result, sound diffusers will make a room more lively as compared to sound absorbers.
Sound absorber vs. sound diffuser comparison chart
| Sound Diffuser | Sound Absorber | |
| Properties | Reflection And Dispersion Of Sound | Absorption And Isolation Of Sound |
| The Material It Is Made From | Wood, Polyurethane Covered In A Hard Coating | Various Materials Such As Wool, Fabric, Cloth, Foam, Rubber, Etc. |
| Application Used For | Acoustics Sound Purposes | Acoustic Sound Purposes |
| Based On | Mathematical Principles | Converting Sound Energy |
| Size | Approximately 1 Meter Squared When Averaged | Size Can Vary From Entire Walls To Panels To Block And Boxes Of Various Sizes |
| DIY Capability | Moderate To Difficult | Relatively Easy |
| Can It Be Used On Its Own | Yes | Yes |
| Can It Be Paired With Its Opposite (Diffuser Or Absorber) | Yes | Yes |
| Does It Work Well For Reflecting Sound | Yes | No |
| Does It Work Well For Absorbing Sound | No | Yes |
| Does It Work Well For Isolating Sound | No | Yes |
Hence one is not better than the other, but each offers its own take on acoustic properties that you can utilize to achieve the best overall sound in a particular space.
Check out these sound acoustic diffusers on Amazon here
Check out these sound acoustic absorbers on Amazon here
We have not chosen to select any one specific diffuser or absorber that you should go for because in the end, you will need to understand the acoustic properties of your space is and all areas, spaces, and rooms are different.
What is a sound diffuser?
This is a specific type of acoustic panel used in audio environments. A sound diffuser is specifically designed to treat reflections and echoes.
These acoustic panels do not absorb sound but rather disperse it, preserving the room’s liveliness by making the sound diffuse (spread) throughout the room.
In a perfect world, a sound diffuser will act, causing an incident sound wave to spread in any direction evenly. Their art like shapes and patterns usually identifies them even though these types of constructs are designed with a purpose in mind and not just to look like something out of a sci-fi movie you would hang on your walls.
What does a sound diffuser do?
In detail, a sound diffuser will treat sound aberrations such as reverberation and echoes in a room, hall, or theatre. Due to the fact that they do not remove sound energy but rather disperse and diffuse it, they are a fantastic substitute or even great alternatives to sound absorbers.
They effectively cancel out or rather reduce distinct echoes and reflections (reverberation) while still ensuring and maintaining an impacting liveliness to the sound quality.
What can sound diffusers be made of?
Sound diffusers can be made of various materials such as polyurethane covered with a hardening layer; otherwise, the other most common material is wood.
This is because you need a hard material that can reflect sound. Soft, absorbent material won’t do, and those types of materials will be used for sound absorbers rather.
What different types of sound diffusers can you get?
There are five main types of diffusers, and they are all designed using mathematical formulas to obtain their shape and look so as to try and disperse sound in a particular way,
Maximum length sequence diffusers (MLS diffusers)
These types of diffusers are manufactured with strips of materials that have two different depths to them. To obtain the maximum scattering effect of sound, the width of the strips is smaller than or equal to half the wavelength of the frequency.
Ideally, small vertical walls are placed between lower strips improving sound dispersion. The one thing to note is that these types of diffusers are limited to one octave above the design frequency.
Quadratic-residue diffusers
Not being satisfied with MLS diffusers, designers wanted to combine the fantastic dispersion characteristics of the MLS design with a broader bandwidth, and hence quadratic-residue diffusers were born.
These diffusers have a specific design in that they are able to disperse (diffuse) sound in two directions, unlike an MLS diffuser.
In terms of their look, they are very similar to MLS diffusers except that the material range’s strips and depths create hill-like patterns.
Primitive-root diffusers
Primitive-root diffusers are based on modular mathematics. In more detail, they are based on a number-theoretic sequence, which is based on primitive roots.
These diffusers are designed with a notch scattering response in mind; however, the notches are over too narrow a bandwidth to have any impact. They mimic quadratic-residue diffusers in their ability to diffuse sound with similar performance.
Optimized diffusers
With the aid of numerical optimization, diffusers with a small number of wells per period (section) are able to increase the number of theoretical designs.
This means that they are able to have variations in terms of their look. This bodes well for style and architectural designs. Optimized diffusers have a similar response to that of quadratic-residue diffusers.
Hemispherical diffusers
Unlike the previous designs of diffusers, these diffusers are created to disperse sound in a hemispherical pattern. They tend to create big sound in a small room and help control the direction of dispersion in rooms that really need it, such as studios and mixing rooms.
The pattern or rather design of these diffusers looks like a grid, whose cavities have wells with varying depth.
Where do you place a sound diffuser?
Sound diffusers are usually placed at the reflection points in a room. With regards to a studio or mixing room, they are typically placed on the back wall and on the ceiling between the sound source and listening position.
You will need to treat early reflections from nearby boundaries for a more detailed approach once you have placed diffusers at your first reflection points.
What is a sound absorber?
A sound absorber is a type of audio panel or material that is used to block sound both from entering and exiting an area of audible range. It hopes to block and dissipate the sound frequencies before they reach your ears.
What does a sound absorber do?
Unlike a sound diffuser, the disperses and scatters useful sound absorber traps, soaks up, and dissipates (wastes) the sound rather than reflecting it in a more controlled manner.
The two main aspects of a sound absorber are sound isolation and sound absorption. As we said, a useful diffuser disperses the sound keeping the quality of the sound energetic in a way while isolating and negating the sound is the correct property of a good sound absorber.
When used correctly, the sound in an area or room will sound as if it is dead and flat, having no room to travel in. The sound will fade away quickly, and there will be no echo or reflection of the sound emanating in the area at all.
What can sound absorber be made of?
Sound absorbers are usually made with a variety of materials that consist mainly of fabric and foam. Heavy thick fabric and foam are suitable for dampening and dissipating sound.
However, almost all materials except reflective hard materials (wood, concrete, tiles, etc.) will absorb sound such as curtains, blankets, couches, carpets, and so on.
For our purposes, however, we are describing commercial sound absorbers, which are usually square in shape and, as we said, are made from thick foam or material that is fabric-wrapped.
These materials will give us the correct properties that we need in order to convert sound energy and dissipating it in the process.
What different types of sound absorbers can you get?
The three main types of sound absorbers are resonance absorbers, membrane absorbers, and porous absorbers.
Porous sound absorbers
These absorbers are very effective at absorbing sound. They effectively convert sound energy into heat so that only a tiny amount of sound is reflected.
However, with regards to bass frequencies, they are lacking. It is important to note that these types of sound absorbers are better placed further away from the wall and not directly against it to maximize efficiency. This is especially true if the material being used is thicker such as 50mm soft mineral wool batt.
The optimum distance away from a wall or ceiling for porous sound absorbers is approximately 200 – 300mm away. If placed correctly, then they are able to dissipate frequencies as low as 200hz.
Membrane sound absorbers
These absorbers control and dissipate bass frequencies better than porous absorbers. These absorbers are overlooked to a degree due to the fact that they do not look like they can absorb sound. This is a big misconception.
A membrane absorber is a flat box usually between 100 and 200mm deep. They are mounted to the wall with a thin sheet of plywood and are filled with a light mineral wool filling.
A Characteristic of a membrane absorber includes that when you knock on the front panel, they tend to have a deep tone. This is due to the trapped air combining with the mass of material within the panel.
Unlike porous absorbers that convert sound energy to heat energy, these absorbers convert sound energy oscillatory energy. Thus the main characteristic of a membrane sound absorber is to absorb low frequencies, as we have said.
One thing to keep in mind is that these absorbers will reflect high-frequency sounds.
Resonance sound absorbers
The energy process used in these types of sound absorbers is converting sound energy to mechanical oscillatory energy. The principle of how a sound absorber works is when the oscillating system, which comprises air, oscillates around an area. This mechanism is also called a Helmholtz resonator.
In its ideal form, a resonance sound absorber would only absorb one frequency. However, in a world where the human audible range is from 0hz to 20khz, we need to make exceptions; otherwise, there would be thousands upon thousands of resonance sound absorbers for each frequency.
We would use perforated plasterboard for our purposes (which is room acoustics), but you do get other types such as perforated metal corrugated sheets and metal boxes.
This absorber due to the fact that it has a porous absorber in the cavity behind the plasterboard will also act similarly to a porous absorber.
Where do you place a sound absorber?
As with sound diffusers, it is best to place absorbers at key reflection points. You would only be able to do this with commercial membrane and porous absorbers, however.
Remember that resonance sound absorbers are usually built from plasterboard and are typically incorporated into the floor or walls, as with membrane absorbers if they are so built with the room’s architectural structure.
After you have covered the first reflection points in the room, it would be best if you make all the significant points in order that.
One place where you could totally cover the area with absorbers is in a vocal booth. This is because you want complete isolation and absorption for the flattest and most “dead” vocal recording you can get.
How do I know which are the significant reflection points in the room for absorbers or diffusers?
As we have said, both sound absorbers and diffusers should be placed at the respective significant reflection points in a room. Typically if you are in a studio, this would be the back wall because this is the main area on which the sound bounces off.
After that, I would suggest placing diffusers or absorbers situated at directional points away from your speakers or sound source, which would include walls and ceilings.
One important thing to consider is that corners of rooms are prone to have high bass frequencies, and they tend to get trapped there and cause somewhat of a boom. You should consider putting a bass trap (absorber or diffuser) in the corners of your room to prevent this.
This is a basic tip and detailing exactly how you would layout your diffusers or absorbers would depend on the shape of your room, the layout of your equipment, and a few vital other factors beyond this article’s scope.
Conclusion
We now know that there is quite a massive difference between a sound absorber and a sound diffuser; however, they are compatible with each other, and when used in conjunction with one another, they can produce the optimum acoustic treatment giving you the perfect acoustic sound necessary for your needs.
To recap, a sound absorber is built, designed, and structured to isolate and absorb sound as the name would suggest, and there are three different types that include resonance, porous, and membrane absorbers. The principle concept of an absorber is to convert sound energy into another type dissipating the sound.
A sound diffuser is utilized when you still want to capture the excitement and liveliness of the room’s sound quality but do not want any excess reflections and aberrations such as echoes.
You would typically see these being used in theatres, concert halls, on a large scale, and in studios paired up absorbers to enhance acoustic clarity.
So if you are looking to purchase either a sound absorber or a sound diffuser, you should do yourself a favor and check out both because, in the end, both would benefit you more than one would.
