For architects who don’t want to specify the ubiquitous fabric faced acoustical panels, we often recommend acoustically transparent materials in front of fiberglass. These systems can work as well as the classic fabric wrapped panel, but have an entirely different look. The facings are perforated or porous and allow sound to pass through them to the acoustical surface behind.
One porous product that may not come to mind at first is open cell stabilized aluminum foam panels, and therefore they hold unique design potential for a showcase space.
For example, my partner Nate Sevener designed the auditorium acoustics in the Meinel Optical Sciences Building at the University of Arizona where these panels were installed over the walls.
http://www.archdaily.com/130522/meinel-optical-sciences-building-richardbauer/meinel-auditorium-side/
One advantage of acoustically transparent panels is the ability to provide a uniform look over the entire room while acoustically treating only the surfaces necessary. In other words, acoustically absorptive and reflective backings can be located where needed to properly shape the room acoustics while allowing architects freedom to achieve the desired aesthetic.
For acoustical transparency across the full spectrum, it is best that the pores of the material be small and densely packed. The material should have a minimum open area of 17%. This requirement is dependent on the size of the pores and the specific sound absorbing performance that is needed. Materials with larger pores may need to have a higher percentage of open area. When the facing material has very small pores or when reduced high frequency sound absorption is acceptable, lower open areas may suffice.