How Architectural Wood Grilles Affect Acoustics and Aesthetics at Weitz Center for Creativity at Carleton College

A key feature of the acoustic and architectural design of the new Kracum Performance Hall at Carleton College’s new 56,000 SF addition to the Weitz Center for Creativity is patterned wood grilles which accomplish two goals: to allow sound to pass through the grilles to reach hidden retractable sound absorbing curtains, and to create a memorable and architecturally attractive space. AD worked closely with HGA Architects to develop the wood grille design. We also collaborated with students at the University of Hartford to measure the sound transparency and sound absorption of representative wood grille samples, so that the effect on the acoustics in Kracum Performance Hall could be assessed. The 400 seat performance hall incorporated the transparent wood grille panels on nearly all visible wall surfaces; the size, shape, and placement of the perforations in the wood, as well as the way the panels are alternately angled within the room have been done in a semi-randomized way, to prevent an audible anomaly known as “comb filtering” that could degrade the listener experience.
The research was performed in the Paul S. Veneklasen Research Foundation (PSVRF) Anechoic Chamber at the University of Hartford by Nicholas Roselli, Tyler Cotrell, Paul Mangelsdorf, and Jacob Ott under the direction of Dr. Robert Celmer and Dr. Eoin King. The tests were to measure the acoustic transparency and sound absorption of the wood grilles. The wood grilles were shown to be completely transparent for sound below 5000 Hz, whereas above 5000 Hz the transparency is reduced by a few decibels. Although some comb filtering was observed, upon averaging over many sources, the problem goes away. This suggests that in the concert scenario, for an ensemble of multiple musicians, this anomaly will not be a noticeable problem. The grilles were found to only have a marginal effect on sound absorption: the wall or curtain behind instead being the controlling factor. These results present strong evidence that the wooden grilles perform as designed and accomplish their acoustic goal in Kracum Performance Hall.