Sound can be absorbed, reflected, or diffused. To absorb sound, we need to change the electromechanical energy of our sound systems to heat energy. Through this exchange process, using sound absorption techniques and materials, sound energy is converted to heat. This conversion process results in lost sound energy and thus sound absorption occurs.

Sound diffusion does not require any energy conversion. Sound diffusion takes the existing energy and through the use of a diffusor, spreads that energy out in different planes or fields. A quadratic sound diffusor with a vertical array of wells or troughs, spreads sound out in a horizontal plane or field. A sound diffusor with horizontally positioned wells or troughs, spreads the sound energy that enters into it out in a vertical array or field. Both vertical and horizontally positioned quadratic sound diffusors create a two dimensional sound field.

Quadratic sound difusors consists of a series of wells or troughs at different depths but same well widths. Each well or trough depth in the quadratic sound diffusor accounts for a particular frequency group. Each well depth conforms to one quarter wavelength theory. Well widths in a quadratic theory diffusor conform to one half wave length theory.



The dictionary defines acoustical as ” of or relating to sound, the sense of hearing, or the science of sound.” Lets look at each one of these phrases.

Defining acoustical as “of or relating to sound” starts the process. We try to design our environments that we live and work in with our relationship to sound in mind. Sometimes our sound “relatives” are hard to relate to and we have to absorb some of their excesses with sound absorption technology. Sometimes, we have to diffuse their energy by seperating and spreading their energy out many directions, so there is less energy to deal with in certain room areas. This technique can also work with human relatives.

Defining acoustical as “the sense of sound”, hopefully, refers to our actual human sense of hearing. Binaural hearing is our chosen methodology for capturing sound energy and processing it into our brains. Our brains then apply localization and pressure filters to help our brain understand the sound energy and where it is coming from. The sound localization filter is also attached to the eyes. Hearing and seeing are tied together, probably for survival purposes.

Defining acoustical as “the science of sound” is probably the most accurate of all the dictionary definitions. The science of acoustics explains why sound acts the way it does, and how our brains interpret it. Defining how sound acts the way it does is one thing; explaining how the brain interprets the data is very complicated and has its own diciplinary name. It is called the science of psychoacoustics.


Acoustic Panels

Acoustic panels can take many forms. Acoustic panels can be made from sound absorptive or sound diffusion type materials that are arranged in a certain way to create sound diffusion that operates in both a horizontal and vertical plane.

Acoustic panels that are sound absorptive in nature can be made of foam, insulation type material, or as it is called in the building trades fiberglass insulation. Different materials can have different rates and levels of absorption. One must know the frequencies that absorptive materials work at in order to pick the appropriate acoustic panel for the particular application one is using.

Sound diffusor type acoustic panels must have materials arranged in a certain length and height to allow for sound frequencies to be diffused back into the room. Sound diffusors reduce the unwanted room boundary reflections by sending the energy from the reflection back into the room spread out in a fan like array. Acoustic panels that have vertical arrays, diffuse sound out into the room in a horizontal direction. Acoustic panels that arrange diffusion elements in a horizontal array, diffuse sound in a vertical direction. One can create a two dimensional sound field by installing both vertical and horizontal diffusors.


Ceiling Panels

When it comes to room surfaces that we must treat with an acoustical solution, the ceiling is a popular choice. To treat the ceiling we use a series of different ceiling panels that use sound absorption or sound diffusion technology.

We can use absorption to treat the ceiling. There are ceiling panels that contain a sound absorbing material that is used in insulating homes for heating and cooling purposes. We can use a ceiling panel that is covered with acoustical foam. The acoustical foam can be purchased in many different colors.

Another popular method that is available is to use is sound diffusion instead of sound absorption. Sound diffusion spreads out the reflection in many directions instead of absorbing the excess energy as with sound absorbing panels. Sound diffusors add “air” to our presentation without making the room too dead. Ceiling panels that contain sound diffusors are more difficult to design and manufacture.

Ceiling panels are available with sound diffusion and sound diffusion technology built into them to control unwanted room reflections.


Sound Absorption Solution

July 20, 2011 No Comments

Sound is absorbed, diffused, or reflected. Reflections from room boundary surfaces can confuse our stereo or home theater sonic presentation at the listening position. One way to minimize reflections is to use a sound absorption solution. A sound absorption solution to this reflection control issue is probably the most common approach used because sound absorbing […]

Noise Barrier

When we refer to noise, it is usually in the context of unwanted sound energy. The word noise has a negative connotation. Most of life’s noise we want to keep out of our rooms or contain the noise within the room or space it is generated in and keep it from leaking into other rooms.

A noise barrier would refer to some type of system which would prohibit noise from leaving or entering a room. A noise barrier technology is not to be confused with sound absorption technology. Sound absorption technology deals with absorbing energy inside of a room. Noise barrier or any sound barrier technology refers to the inhibiting of sound from entering a room or leaving the room and going into adjacient rooms or structures.

Noise barrier technologies are complicated and difficult structures to build. One must isolate the mechanical vibrations that sound produces through a series of layers of different materials and air spacing. Most noise barrier technologies must be physically decoupled from existing structures, so that sound vibrations are not transmitted to surrounding structures.


Sound Insulating Panels

The term ” sound insulating panels” is confusing. Sound is either reflected, absorbed, or diffused. I do not know any sound that is insulated. I think people want to be “insulated” from sound or a better term would be isolated from sound energy. They just don’t want to hear the bass.

Maybe the term sound insulating panels came about because a lot of acoustical absorbing panels in the marketplace today are filled with fiberglass or glass wool insulation. People then began to equate fiberglass, steel wool, with housing or building insulation and the quiet their homes exhibited. Thus, the term sound insulation panels was born.

Sound insulating panels should be changed to sound absorbing panels. We don’t want to insulate sound, we want to absorb, diffuse or reflect it. We can insulate our homes, but lets leave sound where it belongs.


Sound Barrier Technology

Sound barrier technology refers to the ability to keep the sound in a room from spilling over into existing rooms or structures. It also refers to the ability of a structure or room to keep outside sounds from entering the room. Sound barrier technology refers to the physical characteristics of materials and how they are arranged to prevent sound and vibrations from transmitting through them.

Sound barrier technology consists of materials that have different densities and these materials are arranged in a manner that contributes to reducing vibrations from the electromechanical energy of speakers and any other sound generating device. It is the arrangement of these materials and their respective densities that is the key to producing a good sound barrier. An air space between the layers of different materials is also used to isolate vibrations.

The best way to isolate sound is to build a structure within a structure that is decoupled physically from each other. The Russian doll with a series of smaller dolls inside is an example of good sound barrier technology. Each doll is a separate physical structure set within another doll.

Sound barrier technology has a rating called STC. STC stands for sound transmission class and refers to a structures ability to minimize sound transmission through it. A STC rating of 55 would be a good rating for a door in a recording studio. A STC rating of 60 would be a good rating for a wall within that same studio.


Bass Traps

Bass traps are designed to absorb low frequency energy in our listening, home theater, and professional recording studios. There are two major types of bass traps currently on the market: membrane and diaphragmatic.

The first type of bass trap you will see companies offer is a membrane type absorber. This is a box or cavity that is a certain depth that also has a membrane or cover stretched over the absorber itself. The membrane is cosmetic and is used to cover the contents of the absorber which is usually some type of construction, insulation type, material. The unit itself is constructed of light weight materials. The performance of a membrane absorber is determined by the depth,size, and insulation type material used inside the absorber.

The second type of bass absorber used today is a diaphragmatic absorber that has a face that moves in response to sound pressure exerted upon it. It moves like a speaker cone with a back and forth motion. It movement is not as pronounced as a speaker cone, but it does move in response to low frequency pressure. Inside the diaphragmatic absorber, we can find fiberglass insulation type materials or specially designed materials that lower the pressure level inside the cabinet itself. The cabinet is made to be very rigid to encourage the diaphragmatic face to “move” without the cabinet itself moving.

Membrane type low frequency absorbers are light weight. They are not designed to go down to the lower frequency range even though the manufacturers claim they do. Diaphragmatic absorbers are heavy, but absorb much lower frequencies at greater rates and levels.


Sound Absorption vs. Soundproofing

Sound absorption deals with the absorption of energy within our room boundaries. Our room is a vessel into which we put sound energy in through the use of amplified sound. If we have too much sound energy for the room or “vessel” to handle, we must reduce that sound energy through sound absorption. Sound absorption technology deals with the sound energy within the room itself.

This is true for all frequency ranges. Excess low frequency energy into our rooms causes numerous listening issues. Specially designed sound absorbers must be used to control this type of energy in our rooms, so the low frequency energy does not smother the other frequency ranges. Middle frequencies are important in the accurate portrayal of our vocals. A balance of sound absorption and sound diffusion works well for mid range frequencies. High frequencies are usually controlled through the use of sound absorbing foam technology.

Soundproofing refers to the energy within our rooms and also to the energy outside our rooms. We use soundproofing technology to keep noise outside our rooms from entering our rooms and interfering with our speech or musical presentation. Soundproofing technology can also be used to keep the energy within our rooms from “bleeding” into other rooms or adjacent rooms. This is especially true for low frequency issues or “bass boom”. Soundproofing technology is complicated to design and expensive to implement. One has to spend a lot of money in soundproofing materials to affect a small amount of change.