Controlling sound in exposed structure spaces

Creative ceiling designs do not have to be sacrificed in an exposed structure as evidenced by this dynamic sunburst design. The ceiling panels are backed with an acoustic fleece for noise control.

Acoustical shapes
Acoustical shapes are similar to acoustical clouds, but consist of only a single panel. Ceiling grid elements or perimeter trim are not required. The portfolio includes a multitude of standard shapes, ranging from squares, rectangles, and circles to trapezoids, hexagons, and both convex and concave contours. Custom shapes are also available as well as standard and custom colors.

Designed for use in exposed structures and other areas requiring spot acoustics, acoustical shapes can be installed as individual units or grouped together to create innovative visual combinations helping define the area below.

Acoustical shapes are quick and easy to install and adjust to desired hanging heights and angles. Installation does not require special tools or techniques. The panels are simply suspended from the building structure using a hanging system. The hangers are made from aircraft cable to provide a sleek, clean finished appearance. All hardware, cables, and other required installation components are usually packaged with each panel.

Case study
To house students in a unique, new interdisciplinary curriculum, officials at Zionsville High School in Zionsville, Indiana, decided to renovate an existing 836-m2 (9000-sf) warehouse that had no interior walls and an exposed structure.

“The design challenge became how to define areas within such a large space without building walls,” says project architect, Allen Cradler, of Fanning Howey, Indianapolis, Indiana. “Using the floor was a possibility, but it was definitely the ceiling plane that offered the most opportunity.”

Another aspect of the challenge was to design an eye-catching ceiling with a custom look, but create it with standard products to stay within budget.

To attain the desired aesthetics and acoustics, the design team selected acoustical shapes. The panels were offered in 10 geometric shapes, allowing Cradler to use different shapes to define individual areas.

Groups of convex and concave panels were placed over student work areas, while circles were featured in the entryway, and combinations of squares and rectangles highlight the pathways. By the time the ceiling design was complete, Cradler utilized five different shapes in 36 groupings, totaling 155 individual panels.

“Another feature we liked was the shapes came out of the box finished and ready to go,” Cradler says. “All we had to do is hang them. Ease of installation was a definite factor.”

Acoustical canopies
Acoustical canopies also reduce noise and reverberation time in the space below them, but are very different in size and look compared to acoustical clouds. In terms of size, pre-packaged cloud systems are usually available in squares and rectangles ranging from 2 x 2 m to 4 x 4 m, while acoustical canopies are generally smaller ranging from 1 x 1 m (3 x 3 ft) to 1.2 x 2 m (4 x 6 ft).

Visually, acoustical clouds are flat, while canopies are curved and can be installed as hills or valleys. The most common acoustical canopies are made from mineral fiber. Wood and metal canopies are also available, but must be perforated and backed with an acoustical fleece to obtain the desired acoustical performance.

The ability of canopies to combine an aesthetically pleasing visual with sound absorbing properties that provide spot acoustics makes them ideal for use in exposed structures as well as over individual spaces such as workstations and reception desks.

Installation is easy, requiring no special tools or techniques. The canopies are simply suspended from the building structure. In addition, all hardware, cables, and other required installation components are normally packaged with each canopy.

Direct-to-deck panels
In addition to the use of “free-floating” ceilings, noise issues related to exposed structure designs can also be addressed in several other ways, including acoustic elements that attach close to the exposed deck. Called direct-to-deck or direct-attach ceilings, these panels are specifically designed to maintain the look and feel of exposed structure designs while providing excellent sound absorption. They are offered in three versions: mineral fiber, fiberglass, and cementitious wood fiber.

Most mineral fiber direct-to-deck ceiling panels have a noise reduction coefficient (NRC) of 0.75, meaning they absorb 75 percent of incident sound. They are fast and easy to install on hat tracks or furring strips, and cut easily to fit any space. Aesthetically, the panels attach to the deck of an exposed structure space, allowing them to provide acoustical absorption while virtually disappearing into the space.

Figure 1: Exposed structure acoustical options vs. continuous ceiling.

Ideal for use when retrofitting or making acoustical corrections to existing spaces, the panels usually measure 0.6 x 1.2 m (2 x 4 ft) in size and are available in white, black, and field paintable. Field paintable panels have an unfinished, factory applied scrim that can be painted to match the deck while still maintaining their acoustical properties.

Fiberglass direct-to-deck panels feature an exceptionally high NRC of 0.90. As a result, when installed over only 20 percent of an area they can reduce unwanted reverberation by 50 percent.

Ideal for use in new construction, fiberglass panels are also a simple, affordable way to retrofit poor acoustic-performing exposed structure spaces. They are especially well suited for open offices, educational spaces such as labs, cafeterias, and gymnasiums, and retail establishments.

The lightweight panels are offered in a variety of sizes, providing a wide choice of layouts. The panels can be installed “tight” to an exposed deck to maximize the height of the space and in either long runs, grouped together, or placed individually based on acoustical need.

Cementitious wood fiber direct-attach ceiling panels combine an NRC up to 0.85 with a unique textured look and superior abuse resistance. The high-impact properties of these acoustical panels make them a good choice for heavy use interiors of commercial, institutional, recreational, and industrial buildings.

Wood fiber direct-attach ceiling panels are generally offered in their natural color, painted white, or custom colors. The panels can be painted in the field up to six times without reducing their acoustical properties. They can be attached to a variety of substrates including the underside of the exposed roof deck, the joists, and other commonly used support systems.

Case study
The acoustics in Temple University’s School of Architecture in Philadelphia were exhibiting excessively high reverberation times, affecting students’ ability to hear and understand their instructors. Acoustical testing by Metropolitan Acoustics of Philadelphia confirmed reverberation times were higher than recommended.

Consultant Graham Everhart of Metropolitan explains his team created models based off the testing to develop solutions.

“Our overall recommendation was to incorporate acoustically absorptive materials on the available surfaces,” he says, “and in most spaces, the most available surface was the ceiling, so we focused on that.”

The consultants then collaborated with Nelson, the Philadelphia architectural firm responsible for the retrofit project. “Considering the amount of hard surfaces, from an exposed metal deck and drywall walls to sealed concrete floors, it was easy to see why sound bounced around so quickly,” notes Scott Winger, AIA, technical director for Nelson.

To reduce reverberation time and improve speech intelligibility, the design team chose fiberglass direct-attach panels for the lecture halls and other presentation spaces and wood fiber direct-attach panels for the classrooms and studios. “Both panels perform in a similar manner acoustically, but we went with the wood fiber panels in the classrooms and studios because they were a little more rugged and better suited for these types of spaces,” Winger says.

Acoustical testing by Metropolitan following installation of the ceiling panels validated the choice of treatments. Reverberation time dropped an average of 56 percent in the eight spaces tested, including a 79 percent drop in one of the classrooms and a 64 percent drop in one of the studios.

“By installing the panels between the metal joists, we were able to maintain the look and feel of the exposed structure the university desired while mitigating the reverberation time, which it also desired,” Winger explains.

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