Archive for category Diffusion
Throwback Thursday: Diffusion Vs. Absorption
Posted by Acoustics First in Absorption, Diffusion, Product Applications on May 22, 2025
On this Throwback Thursday, we look back at a popular Sound and Communications article about why sound diffusion is so much more complex a phenomenon than sound absorption. In this article, we discuss some of the different variables associated with the quantification of diffusion – magnitude, phase, frequency, direction, etc. When comparing its properties against absorption, which is simply the reduction of energy at specific frequencies, the argument is cemented as to why a single-parameter coefficient is insufficient to fully express the phenomenon of acoustic diffusion.
Read the article here:
PDF Version of Sound and Communications Article.
Revisit the original post here:
https://acousticsfirst.info/2020/03/24/acoustics-first-talks-diffusion-in-sound-communications/
Throwback Thursday – Diffusion and Binaural Bob from 10 years ago!
Posted by Acoustics First in Diffusion, Offices, Product Applications, Products, Uncategorized, Video on February 27, 2025
In June of 2015, Acoustics First® posted about our experiment which allowed people to hear the effects of sound diffusers in a small space. The experiment consisted of treating a small office with varying numbers of our new (at the time) Art Diffusor® Model D sound diffusers, then providing various sonic stimuli and capturing and measuring the results with a custom binaural head (called “Binaural Bob.”) This experiment received great feedback and with that input, future experiments were conducted using a similar method, mixing absorbers and diffusers, and having a wider range of stimuli.
But here we look back to the first… This is the video we produced during that experiment way back in 2015 with Binaural Bob, a bunch of Model D’s, a small office, some balloons, bang snaps, and one very heavy book.
If you would like to revisit the original post in it’s entirety, here is the link!
https://acousticsfirst.info/2015/06/09/want-to-hear-acoustic-diffusion-audio-demo/
Similar, yet different: HiPer Panel® vs. HiPer Panel® Impact
Posted by Acoustics First in Absorption, Diffusion, Product Applications, Products on December 11, 2024
While the HiPer Panel® and the HiPer Panel® Impact may appear to be identical on the surface, there are some key differences that may change which one you would use, and why you would use it. They are both layered, flat-panel diffuser products, with perforations, and they are both covered in fabric. However, their construction, below the surface, is drastically different. One is a broadband absorber with a modified frequency response which focuses on reduction of specular energy, and cancellation of noise – where the other is a high frequency diffuser and reflector with a tuned bass absorption which is constructed to maintain acoustic energy in the space.
Construction
The HiPer Panel® was originally designed to optimize the capabilities of a standard broadband absorber. Its internal membrane and perforations create a material that works to modify the range of absorption, and create high frequency diffraction… but that isn’t all. The cavities are backed up to the membrane, which changes the reflection characteristics, where high frequencies can be reflected, and higher energy waves are absorbed more than if it was just fiberglass. This extended range is random, as the perforation density is gaussian in nature, but the membrane is also randomly backed by more cavities.
This design creates 4 different physical conditions that acoustic energy has to contend with… in a gaussian distribution.
- areas of the panel with 2 layers of fiberglass and a membrane in the middle.
- one layer of fiberglass with a rear membrane over a cavity.
- a cavity with a membrane back… sitting on fiberglass.
- a cavity with a membrane back… stretched over another cavity.
The random distribution of multiple acoustic obstacles is what gives this device its unique characteristics. It’s an absorber that changes its performance depending on where sound hits it, and at which frequency. Some frequencies pass into the cavities and reflect off the membrane, while others are dampened by the membrane… while longer wavelengths see the membrane as a stretched diaphragm or limp mass.
The HiPer Panel® Impact has a very different construction and may be used for a very different reason. The HiPer Panel® Impact uses the same pattern of holes, but the holes aren’t cut into an absorber… they are cut out of a reflective face, which is attached to an absober. Unlike the first HiPer Panel®, the “Impact” can be used to maintain more of the energy in the space, break up some of the higher frequencies with that gaussian hole pattern, and be a low frequency bass trap. The design is simple and effective, but is not necessarily used in the same places where you would use the first HiPer Panel®.
Use cases.
The first Hiper Panel® is often used in theaters, and listening spaces where focusing on the source is of primary importance. Its broadband absorption, gentle high frequency diffusion, and smooth mid frequency control are ideal for critical listening environments such as mixing rooms, media rooms, theaters, or even voice over spaces. The performance is about removing the acoustic elements that could interfere with the focus on the source speakers.
The HiPer Panel® Impact is often used in performance spaces, where you want to maintain energy, break up high frequency flutter, and remove low bass. The reflective face doesn’t remove as much energy from the space, however it does change the characteristics of the space. This helps break up some frequencies, reduce bass, and keep the energy moving around the room. Music halls, churches, auditoriums, and any space that relies on the room helping to reinforce the sound will benefit from these taking the edge off the highs and dampening the lows – which is how the HiPer Panel® Impact controls the sound… while helping it maintain its “impact.”
In summary, while these two products are in the same family, they have a different core construction, which changes their performance. There are scenarios where you may use them both, however since they address different problems in a space, they are not always interchangeable. Contact Acoustics First® if you have questions about any of our products.
St. Andrew by the Bay – Custom HiPer® Impact Panels to absorb and diffuse sound!
Posted by Acoustics First in Absorption, Diffusion, Product Applications, Worship Facilities on April 10, 2024
St. Andrew by the Bay is a traditional worship facility with a focus on spoken word worship and congregational singing. The large volume and hard surfaces in this space are the physical features most at fault for excessive reverberation, comb filtering and distracting “slap” echoes (discrete sound reflections usually caused by a distant, reflective back-wall).
To correct the slap-back and curb excessive reverb without “over deadening” the space, we recommend distributing approx. 550 SQFT 1” HiPer® Impact absorber/diffuser panels throughout the rear wall areas (see attached layout). HiPer® Impact panels absorb low frequencies and diffuse high-frequencies, yielding a much more even room response. In addition to controlling bass buildup, the high-frequency scattering will help retain some “life” in the room for acoustic and choral performances.
Reverb Prediction – Historically, churches relied on an abundance of hard surfaces to propagate sound to the rear of the nave, so they benefited from very long reverb times (upwards of 4-5s). Modern sound systems allow for a much more focused sound and equitable listening environment , so these extreme reverb tails are no longer necessary and can actually degrade the experience of the congregation. Churches of this size with a sound system and traditional worship services should have a reverb time somewhere in the 1.5-2.25s range. We entered the sanctuary’s dimensions and construction materials into our acoustic calculator and made a prediction of reverb times before and after treatment.
From Lee Hartman & Sons who performed the install “Here are some photos of the finished panels at St. Andrew by the Bay. It turned out great and client is very happy. Many thanks to Cameron for the detailed layout.”
Similar, Yet Different: Model C vs. Model D!
Posted by Acoustics First in Diffusion, Home Entertainment, Home Theater, Media Room, Multipurpose Rooms, Music Rehearsal Spaces, Music Tracking Room, Product Applications, Products, Recording Facilities, Recording Studio, Studio Control Room, Theater on January 5, 2024
In this installment of “Similar, Yet Different,” we take a good look at two very different looking diffusers in the 2’x2′ size… the classic ArtDiffusor® Model C and the organic, rippled ArtDiffusor® Model D – while there are some similarities, there are some key differences in how they look (obviously) and how they perform.
Quick Similarities.
The ArtDiffusor® Model C and Model D are both 2’x2′ diffusers which are made to be either wall mounted or installed in a standard drop-tile ceiling grid. They are both formed from a Class A fire-rated polymer in a single piece. Both are mathematical diffusers, which create their different physical features in a “form follows function” methodology. They also cover roughly the same frequency bands, with some minor variation in how they execute their control.
Difference in Math
The Model C is an interesting configuration. Often you will see quadratic residue diffusers with flat blocks or wells in a relatively standard quadratic cell formula configuration. The Model C runs in a much different alternating binary configuration. The basic idea is that cells are placed in a 45° array with each cell adjacency calculated as an alternating array of higher and lower cells starting in the middle and working in a pattern of alternating low/high cell clusters decreasing toward the edges of the diffuser. These diffusers also do not have flat tops on the blocks – they are angled at 10°. The orientation is then rotated in 90° steps in a pattern that maximizes the spatial redistribution of reflected sound. This was a vast design departure over the original quadratic design, and created a diffusion profile that was distinctly different.
The Model D was an even greater departure. It began with a Maximum Length Sequence (MLS) concept that first changed the varied straight channels into rings of different dimensions. These rings then broke from the MLS mold by getting varied height profiles based on the QRD sequence. As if having different size rings at different heights wasn’t enough… the randomness was further perpetuated through a Boolean process of assigning certain rings a random property that would either add or subtract height from any other ring that they crossed. Finally, the entire surface geometry was smoothed using a bicubic interpolation, creating the organic undulating surface which gracefully spans the entire profile.
What this difference in math does to the acoustic performance.
The Model C has a nice even diffusion profile through it’s primary working range. This is a product of the QRD design and binary distribution. The set size for the blocks guarantees a solid primary frequency range from about 1KHz to over 4Khz. This tunes the Model C squarely in the most sensitive bands of the human hearing range. Below this range the device becomes a bit of an absorber. Above this range and the performance becomes more effective at intervals, which can be seen in the areas of wide diffusion at 6KHz – 18 KHz. These repeating zones are common in “stepped” quadratic designs. Due to the heights of the well being at specific intervals, the intervals repeat at octaves of their effective bands.
The Model D doesn’t have the same stepping. The spline interpolation and the random Boolean shifts smooth the transition from one quadratic height to the next, and the MLS sequence causes a bit of a high-pass filter pushing the start of the primary range to around 2KHz – which is a little higher than the Model C. The main difference is that once the Model D starts it’s range it diffuses everything up to and over 20KHz without the banding that can happen in other quadratic designs.
Another difference in symmetry.
The ArtDiffusor® Model C is a fairly symmetric design, but it’s 45° angle pushes that symmetry along the diagonal (corner to corner) across the unit. The asymmetry is subtle but allows for enough variation to account for any “lobing” issues that can occur in more simple geometric devices The 10° block faces being at varied orientations is key to increasing the spatial directivity over the older “flat-faced” Quadratics. This was a very novel design when it was first introduced, and those benefits are crucial to the longevity of the Model C’s reign – It just works. It’s predictable and musical… and that’s why it’s here to stay!
The ArtDiffusor® Model D is a completely different animal from the Model C when it comes to symmetry… as a matter of fact… there isn’t really much on it that is symmetric! The Model D was designed as a departure from symmetry. Focusing on the mid to high frequencies, which are very specular, the organic geometry creates an asymmetric reflection pattern. This pattern can be used to steer the sound into a wider field.. and that profile changes with the wavelength of the sound that hits it. This steering ability and the wide frequency range has made the Model D a favorite in mixing and mastering environments, where they can get smooth performance through the entire frequency spectrum.
How these differences benefit everyone.
We have stated before that there isn’t really a one-size-fits-all solution in acoustics. Many environments will use various treatments to achieve their desired goals. You will often have different devices to address different problems, in different frequencies, in different locations, in the same space. Bass traps for controlling the lows. Absorption to reduce gross energy across the board. Large geometric surfaces to break up parallel reflections and steer the projection of sources. Mid range diffusers to create clarity to the sources and reduce artifacts. High frequency diffusers to reduce flutter and add a feeling of envelopment and airiness in the space. These devices all have their place – from the smaller listening rooms, to critical listening environments, and large multifunction spaces and venues.
It is also worth noting that these two devices have a very different aesthetic visually. The classic blocks of the Model C have become a signature look for quality sound environments, and people recognize them as they would classic geometric pyramids and barrels. The Model D aesthetic provides a visual accent that people take advantage of to set their space apart from others. The undulating, asymmetric pattern changes drastically when you rotate the individual units in the array. This allows for not only varied acoustic performance, but also a unique visual possibilities – with numerous variations.
The ArtDiffusor® Model C and Model D are two tools that are used to craft ideal listening environments around the world… and in those roles they are indeed Similar, Yet Different.
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