RPG Diffusor Systems

RPG Optimizes the Main Theater of the National Museum of the American Indian

RPG is proud to have collaborated with Jaffe Holden Acoustics and Polshek Partners on the acoustical optimization of the circular main theater in the National Museum of the American Indian.

Early rendering of main theater

Vertical wood paneling surrounding the 322 seat circular theater, evoking a dense hard wood forest, and above a dark blue ceiling twinkles with constellations. Like many of the spaces, the auditorium engages all of the senses. The main theater is a storytelling vehicle: a clearing in the forest under the night sky. Indeed, this space in the round with its vertical textured and detailed wood walls conjures up a pine forest, and the midnight blue acoustical ceiling, replete with twinkling “stars,” completes the effect. A surrounding lateral aisle allows actors into the audience, a necessary component of many American Indian performances.

Acoustician Steve Haas, working with Jaffe Holden Acoustics, Norwalk, CT was concerned that the circular room, shown in the RPG model, would provide focusing problems and Damyanti Radheshwar from Polshek Partnership and the design team devised an undulating and tilting façade on the circular walls, which was very rough and diffusive in the rear and gradually became reflective next to the screen. This can be seen in the half plan illustration. The design team of Haas and Radheshwar asked RPG to acoustically model the topology of the wood paneling to provide uniform sound diffusion and

RPG model of main theater

Half plan of the main theater showing how the diffusive rear wall gradually transitions into a reflective surface where it meets the projection screen in the lower left of the illustration.

minimize focusing. RPG utilized its proprietary Shape Optimizer to optimized the undulating pattern to provide uniform scattering.

The process involved the use of RPG’s FlutterFree planks interspersed with flat wooden planks, the depth and positioning of each optimally determined by the Shape Optimizer.

The proposed arrangement by Polshek Partnership was evaluated and optimized. The angular response is shown at 1.5 kHz, as well as the diffusion response, which is a summary of the uniformity of the angular response at all frequencies. The final design of a repeating Diffractal section is also shown.

Angular response of original proposed Polshek pattern, an improved similar pattern, an optimized pattern and a flat panel.

Diffractal section pattern utilizing FlutterFree on main theater walls.

Comparison of the diffusion coefficient for the proposed pattern, a flat panel and the optimized design.