Sounding Off: Re-shaping Glass for Acoustic Performance

By Joshua Huff

Most consumers don’t think of glass when it comes to sound control. Acoustic materials, such as wood, steel, acrylic and concrete, vital in the construction of buildings, probably come to mind first. You’ll often find these products in spaces such as studios, reading halls, theaters, and libraries, among others. Acoustic materials help optimize sound as it moves through space. The amount of sound that travels through space can make a drastic difference in the overall experience. And glass can also offer exceptional acoustical performance.

Shaping Glass to Control Sound

A team of researchers set out to discover how glass can be controlled and used as an acoustic material. The team was led by University of Michigan associate professors of architecture Catie Newell and Wes McGee, along with Zackery Belanger. Belanger is the director of the Detroit-based Arcgeometer, a multidisciplinary acoustic architecture studio that specializes in shaping objects, surfaces and rooms.

The idea came to Newell and McGee when they started using techniques to slump glass to induce curvatures in otherwise flat glass.

“This was an interest that paired with some of the more complex geometries that were possible with other materials as new digital fabrication techniques were advancing in the realm of architecture,” says Newell.

Following several glass projects that featured free-form catenary slumping, Newell and McGee discovered that shaped glass created interesting light and sound effects. Intrigued, the two researchers teamed with Belanger to push the relationship between the formal manipulation of glass and how it performed acoustically and optically.

“It was important to us to consider how glass could alter space if we changed the ways we normally work with it,” says Newell.

According to the team’s research paper, “Shaping Glass for Acoustic Performance,” glass is an excellent candidate for advanced acoustic surfaces “due to its visual appeal, relatively low cost, malleability and integrity at many scales.”

Long Range

The team’s interest in manipulating glass to be used acoustically resulted in Long Range, an experimental glass artifact that exhibits the four traditional categories of acoustic behavior —reflection, diffusion, absorption and transmission—all through a change of form via the slumping of glass lites.

Long Range features an acoustic surface comprising 64 hexagonal, slumped glass lites that are arranged in two layers of 32 lites each. Each lite can be perforated with auxetic patterns that change the acoustic properties. The team worked with PrivaGuard glass from Guardian Glass for the project. The purpose of Long Range is to study the shaping of glass for broader acoustic qualities, says Belanger. He adds that Long Range is more about the design possibilities of glass than solving a particular problem.

The team discovered through the project that sound absorption can be accessed through a change in form. They concluded that there was enough evidence for glass and similar materials to be considered “instinctually acoustic.”

Acoustic glass, which is often known as sound control glass, typically is designed to stop sound from traveling through it. Its effectiveness is based on the glass thickness, number of interlayers and how much space is between the glass. Long Range, however, seeks to alter the perception of glass as a sound control material but instead as a medium that can distort and control sound. Despite the experiment, glass still has a few inherent acoustical challenges, says Belanger.

“Glass has a poor reputation acoustically in architecture,” says Belanger. “Visually it is usually used as an invisible barrier. We wanted to show that it can be much more than that.”

Applying Long Range

Belanger says Long Range is intentionally not an applied acoustic system, but a demonstration that room surfaces themselves have innate acoustic qualities that can be controlled. Architects could shape the glass boundaries of a lobby, for example, to reduce reliance on traditional acoustic products. A concert hall could be made of glass and meet stringent acoustic criteria, says Belanger.

“It is possible, as shown through Long Range, that glass can operate along the entire acoustic spectrum, working from reflection and focusing, to diffusion, absorption and transmission,” says Newell. “We don’t usually think of glass as having these behaviors, but if the shape of a material or space is considered from the onset into how it can perform with sound and optics then the malleability of glass works well for creating such behaviors.”

The artifact is currently a prototype that demonstrates variables within a system of making and thinking. As a major surface, it begins to project toward understanding how it can be used for interior and exterior applications, as well as full enclosures.

Newell says that there are no current plans to commercialize Long Range. She says their work has been focused on proof of concept more so than commercialization. As of now, the acoustic influence of Long Range is relatively mild compared with traditional materials, says Belanger.

“Long Range is not meant to be yet another off-the-shelf acoustic product to be applied to spaces,” says Belanger. “It was expensive to produce, but we think that accessing the innate acoustic qualities of materials like glass could have expansive benefits for architecture, especially when the surface addresses enclosure, light and sound simultaneously.”

Joshua Huff is the assistant editor of USGlass magazine. Email him at jhuff@glass.com.

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