Archive for category Diffusion

NWAA Labs goes nuclear in Stereophile

Ron Sauro of NWAA Labs talks about his massive test facility, speaker measurement, sound diffusion, and more in this article in the August 2022 edition of Stereophile Magazine.

Ron Sauro shows off the current configuration of NWAA Labs’ massive Free-Field Chamber – complete with giant anechoic wedges and a 4+ meter arc of microphones, this room could also comfortably nest 4 football fields.

In the article, there is mention of the advances that Jim DeGrandis and Acoustics First® have made in the understanding of diffusion, the developing standards for testing in the ASTM, and their published research into modelling/simulations for refining new acoustic materials.

Read the Article Now!

For more information about this edition, and other editions of Stereophile, visit them at https://www.stereophile.com/

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Absorption & Diffusion – The Construction Specifier

For the May 2022 edition of “The Construction Specifier,” Acoustics First was asked to illustrate the use of absorption and diffusion in creating optimal acoustic spaces. The article is a great reference for understanding the types of acoustic absorbers and diffusers, as well as some use scenarios like offices, critical listening spaces, and larger communal spaces.

Note: This version has been edited and the advertisements are removed. The full published version of the May 2022 digital edition can be found on The Construction Specifier’s website here.

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Sound Diffusion vs. Absorption in Worship Environments

There are many examples of diffusing architectural elements in this synagogue.

Cathedrals, mosques, synagogues and temples are often decorated with an abundance of architectural details (deep coffers, arches, columns, sculptures, intricate engravings etc.). These features are not only beautiful to look at, but also serve the vital acoustic purpose of sound diffusion. Large, uninterrupted spans of hard, flat surfaces reflect sound in a singular, specular wave, which creates discrete echoes and comb filtering (In acoustics, comb filtering is when a delayed reflection interferes with, and distorts the original sound wave). These conditions can contribute to an acoustically uncomfortable environment, in which speech is difficult to understand, and music can be hard to perform and enjoy. Irregular surfaces, on the other hand, scatter these reflections, minimizing comb filtering and distracting echoes. In a “diffused” worship environment, speech is intelligible, music is clear and warm, and there is a sense of envelopment which greatly enhances the congregants’ worship experience.

Absorptive treatment can also be used to control echoes and harmful reflections. Instead of redistributing reflections, these “fluffy” materials (drapery, padded pews, acoustic panels etc.) reduce the overall sound energy from the reflections in the room. However, using to too much sound absorption in a room can often make a space sound ‘dry’ or ‘dead’. Determining whether your space needs absorption, diffusion, or a combination of both is dependent upon the acoustic properties of the space, as well as the type of worship service being conducted.

Acoustic Properties of the Worship Space: Reverberation, a principle acoustic factor, is the sound energy that remains in a listening environment as a result of lingering reflections. The dimensions, construction materials, and furnishings of a given worship space determine its reverberation time (RT or RT60). Large halls with reflective materials (glass, wood, concrete) have longer reverb times, while small rooms with absorptive materials (drop acoustic ceiling, carpet, curtains etc.) will have shorter reverb times. Incorporating sound absorptive materials, Such as fabric wrapped acoustic wall panels, is often the best way to reduce the overall reverberation in a room to a suitable level. However, the target reverb time also depends on the nature of the worship service being conducted in a particular space.

Type of Worship Service: Ideal reverb times for worship environments vary widely.  Non-musical, spoken-word worship requires a very short reverb time (.5-.8s range), ensuring that speech is intelligible. At the other end of the spectrum, cathedrals can tolerate an extremely long reverb time (2s and above) due to the traditional nature of their liturgy. Choir, organ and plainchant worship will actually benefit from longer reverb times that create a sense of ambience and spaciousness by sustaining musical notes. These spaces will often lack a sound system, and instead utilize the hard surfaces to propagate sound throughout the room.

Traditional worship may be enhanced by long reverb times, but contemporary worship requires a significantly shorter reverb time. In these environments, drums, guitars, bass and other amplified instruments are critical to the high intensity worship experience, but have far different acoustical needs compared to the choir and organ in a more traditional service. Contemporary “high impact” churches require a reverb time in the .8-1.3s range to ensure that the music won’t become too “muddy” and indistinct. Contemporary churches must also be more cognizant of late specular reflections (slap echoes) which can inhibit the timing of musicians and contribute to poor music clarity.

Let’s take a look a few common scenarios when it comes to treating traditional and contemporary worship spaces.

While including a mix of absorbing Sonora® Panels and diffusing Double Duty barrels, many people overlook the contribution of the padded chairs and carpet to the sound of this space.

Scenario 1: Conversion from Traditional to Contemporary worship

A growing contemporary church moves into a larger, traditional sanctuary and is confronted by a raucous acoustic environment during their first rehearsal… This “live” space was perfect for traditional music, but is not conducive to a “high impact” contemporary worship service. To reduce the excessive reverberation and distracting echoes, sound absorption should be added to the rear wall (opposite stage) and side walls. Also, if using on-stage monitors, the stage walls should be treated to manage stage volume.  Spot diffusive treatment that provides low-frequency absorption would also be beneficial. A good choice for this would be traditional ‘barrel’ diffusers. These are one of the oldest tried and true solutions for controlling bass issues in a performance space. Also, since these units function as both absorbers and diffusers, you get the benefits of both.

Scenario 2: Mix of Traditional and Contemporary worship services.

A worship facility decides to offer a contemporary service in addition to their traditional services… As more absorption is introduced to cut down on distracting reflections, we want to retain the envelopment and spaciousness which benefits congregational singing and traditional worship music. Sound diffusive treatment would be a great way to control echoes and specular reflections, while keeping the energy in the space. A mix of absorption and diffusion is usually best. Multipurpose spaces can also benefit from variable acoustic treatment which allows the room to “adapt” to each service, but that is a subject for another article.

Scenario 3: Poor Music Clarity in Traditional Worship space

A traditional worship space renovates their facility by adding thicker carpet, padded pews and a drop acoustic ceiling… All of a sudden, their once lively space feels “flat” and dull. Acoustic instruments are more anemic, less distinguishable and choirs have a difficult time blending and tuning.  To “liven up” the space, replace sound absorptive materials with diffusers.  For example, replace 1/3rd of the acoustic ceiling tiles with a combination of gypsum tiles and lay-in diffusers. These days, there are wide variety mid-range quadratic sound diffusers available for drop tile ceiling grids, as well as the more traditional barrel and pyramidal diffusers.  

While this space is more lively, the slap echoes from the back wall are controlled with a mix of diffusers and absorbers.

Sound diffusion can often seem a little mysterious compared to sound absorption. This is at least partly because sound diffusion is a more complex and multi-dimensional phenomenon compared to the more easily quantifiable sound absorption. However, sound diffusion is often times the missing piece of an acoustic puzzle: its benefits can help a bad room to sound good, or a good room to sound great!

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The HiPer® Panel and Ken Fritz’s Dream

Ken Fritz completes his dream theater, and behind the scenes is the HiPer® Panel by Acoustics First®

There are many home theaters of note, but rarely is one created (at this scale) by the singular dream and dedication of one man. Ken Fritz involved Acoustics First® early in the project to perform acoustic measurements of the space, and his theater became the first large-scale installation of our newly developed HiPer® Panel. From beginning to end, Ken says that he spent more than 25 years on the realization of his dream – and others have taken notice.

Ken’s vision had a scale that is rarely seen in home theaters.

There have been numerous write-ups of Ken’s theater, which was constructed (from the ground up) specifically for this purpose. The walls are hurricane grade block construction, the roof-line is constructed to improve the acoustics, the walls are clad in HiPer® Panels, the bass emanates effortlessly from in-wall enclosures – and just look at those custom built arrays that Ken designed and constructed by hand! This project is more than just a labor of love, it is an obsession with excellence.

Even a custom-designed and hand-built turntable feeds Ken’s dream environment.

This obsession covers every aspect of the room and the system, with everything being either built by hand, customized to his specifications, or simply the best you can get! If there is a “home theater mountain,” Ken built a skyscraper at the summit – but don’t take our word for it…

You can watch the one-hour documentary telling the story behind the dream – in Ken’s own words.

Watch the documentary of what has been called “The Best Stereo System in the World.”

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Similar, Yet Different. Double Duty Diffuser™ Vs. Pyramidal

For this installment of “Similar, yet Different”, we will be going retro – The Barrel Vs. The Pyramid!  These two shapes are the historic foundations for modern acoustic treatments.  How did they come about? Why do they work? How are they different?

These two shapes have origins before written history.  The pyramids of Egypt may not have been renowned for their acoustic properties, but they certainly show the historical age of this shape.  The barrel is also an ancient shape, born from the pillars of historic temples and gathering places.  Both of these shapes have been used in architecture for the expanse of human history, and their acoustic properties have been studied in numerous environments, in many different applications.

These shapes are often referred to as “primitive.” The barrel, in its basic form, is a truncated cylinder – basically a segment of the cylinder. The pyramidal is, in this case, a modified/offset pyramid… a pyramid without equal sides.  Their differences begin with this fundamental variable – the pyramid has angled planes and the Double Duty™ is a large curved surface.

Symmetry vs. Asymmetry

Another simple difference is the fact that the Double Duty™ is symmetric and the offset pyramid is asymmetric.  The barrel primarily scatters sound across the curve of the face – sending acoustic energy in a wide arc. However, the pyramid’s facets are all angled slightly differently – reflecting in different directions.  This allows the pyramid to be installed in complex arrays which create more “random” reflections due to their different facet angles.  The Barrel is primarily a one-dimensional diffuser, and installs either horizontally or vertically.

Note that the Double Duty™ (barrel) scatters across the curve of the face while the Pyramid throws energy in different directions.

Diffraction.

There is another phenomenon that helps to contribute to diffusion – and that is diffraction.  Diffraction is what happens to sound when it hits a corner or edge.  Unlike light, acoustic energy is the physical fluctuation of pressure changes – which gives sound the ability to travel around corners.  This bending varies by the wavelength of the sound and the size of the object in encounters.  Both barrels and pyramids have facets which introduce diffraction, and while both can be made in different sizes, the offset pyramid has different sized facets on each device – contributing to more randomized diffraction at different frequencies.

Inverse Square Law

Without getting too heavy into math, as sound travels it decreases in intensity.  This is due to the fact that sound “spreads out” as it travels. It is produced with a finite amount of energy, so intensity drops as it covers more space.  Both the barrel and pyramid increase the rate that sound “spreads out,” which diminishes the intensity of the sound – however, they both do it slightly differently, however..

The Double Duty’s™ curvature leaves the wave primarily intact, but it increases the rate of expansion across the curve.  This redirection is very smooth and predictable, where the random facets of the offset pyramid break up the sound into sections which travel in different directions.  At the intersection of those facets, diffraction takes the reigns and scatters sound even further.

By increasing the rate of expansion of the wave, you decrease its intensity while also breaking up the wavefront which helps to reduce echoes and flutter.  Both the barrel and the pyramid are perfect for larger spaces, as those massive surfaces do a great job of controlling reflections from large wave fronts.  Also, due to their simple shapes, they can be made really big, which helps!

Absorption.

There is one more feature which is sometimes overlooked.  Because of the material of their construction, and the large volume of air behind them, these diffusers exhibit a certain amount of “bass trapping.”  The Double Duty™ diffuser got it’s name due to this characteristic.  It’s not just a diffuser, but also a bass trap.  The Pyramidal diffuser also exhibits bass absorption, though it is slightly less.

So there it is… the battle of the classics!  Sometimes, keeping it simple is the way to go!

 

 

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