This report describes the development of a multifunctional building and the research that supports the design. The question was “what are the characteristics of a multifunctional exhibition hall of which the structural design is integrated with the variable acoustical design and of which the acoustic properties are used as decisive factors in the visual appearance of the design?” Combining acoustical shapes with structural design can lead to intriguing forms. Using computer analysis, literature studies and case-studies a concept design was developed. As a foundation for the design the existing exhibition complex WTC expo Leeuwarden was used. The new hall replaces an existing hall and thus it has to be an addition to the functionality of the building, rather than a replacement. This has been done by not creating a hall only functional as an exhibition hall but as a concert (amplified music) hall, acoustical music hall and speech hall as well. Especially the acoustical music hall should meet very specific acoustical properties. The other functions have different acoustical properties. The exhibition hall requires an empty floor plan, which results in a challenging structural design scope as well. To minimize the amount of materials needed for the structure the aim is to integrate the acoustical shape and materialisation with the structural design. Literature study explains the relation between sound waves, frequencies, reflections and how they contribute to the experience of the audience in a concert hall or auditorium. Important elements for the experience of the receiver of the sound are envelopment, reverberation, clarity and loudness. Envelopment depends on the sound direction as perceived by the receiver. A larger variety of sound directions results in a better envelopment, which is desirable for music related functions. Reverberation time, clarity and loudness can analysed objectively. The current shapes of concert halls are derived from optimization of either view or envelopment, but not both. The rectangular and hexagonal shaped concert halls are the most successful in combining a good view and envelopment. Folding techniques have been inventoried. By folding the roof or wall, a surface is created which can diffuse the lateral sound reflections and create a better envelopment. The angle of the folds and direction of the surfaces strongly influences the envelopment. They function best when the folding lines are parallel to the main sound direction. The exhibition building in Turin, designed by Nervi, shows how a structure with a large span can be reached with a minimum amount of material. Nervi also designed the UNESCO conference building in Paris. This building is an example how structure can be combined with the acoustical shape of a hall. While these projects where used as an inspiration, ‘de Spiegel’ in Zwolle is an example how moving elements and changing volumes can change the reverberation time and clarity of a hall. Based on the literature study and case studies, a concept was developed where a folding technique is used to create the wanted diffusion in the concert and acoustical music hall. While the folding technique also allows the structure to change its shape volume and floor surface. This way the amount of unneeded area is minimized, which reduces the climate demands. The dynamic exterior fits the changing function of the building and results in a dynamic interior as well. To create the dynamic exterior a pattern combining X- and V-folds was used. This pattern is mirrored over the centre of the hall to form the second part, resulting in a three-hinged span. Research shows that, without any additions to the structural design, the best envelopment, clarity, loudness, reverberation and echogram is reached by using 16 of the folded ribs, which have a width of 10 meter when they are unfolded. The folding shape is also a strong structural shape. Glass fibre reinforced plastic is a lightweight material with high tensile and compressive strength and was used to create a structural shell. Due to its poor acoustical insulating properties the material rigid polystyrene foam, which is a common material in sandwich panels, was not used as insulation on the inside of the panel. A hard rock wool, which has a good sound absorption property, was used. Calculations have shown that a thickness of 260 mm was needed to reach a Rc-value of 6 m²K/W. This results in a theoretical Rw-value (sound resistance) of 97 dB. The hinge used for the connection of the composite panels is a longitudinal composite fabric hinge developed by Vosmaer. This hinge is easy to fix on the building site. The hinge does not use any thermal insulation, therefore profiles are added to the outside of the structure to minimize sound leakages and thermal bridges. The side walls of the structure change shape as well. To close off the wall triangular composite panels are sliding over each other. When the structure changes shape, the wall is able to move along. These panels and the structural composite panels can be produced in a large hall using molds. Because of the location of the WTC expo, the composite panels can be transported by ship to the building site. If the structure would be built on a different location, the elements should be made in smaller parts and joined on the building site. The acoustical music hall and the speech hall are designed to be the smallest configuration of the hall. The speech hall has a reverberation time of 0,78 seconds and a clarity (C50) of 2,0 dB. The acoustical music hall has a reverberation time of 2,28 seconds and a clarity (C80) of -0,8 dB, these results are desirable. The transformation between these two functions is achieved by flipping the panels of the internal wall. These panels function as doors at some locations, but their main purpose is to contribute to the acoustical design, as one side of the panels is perforated and functions as an absorbing surface while the other side reflects most of the sound. Panels can be added to the side of the entrance doors to absorb sound as well. When the hall is used for a speech related function a reflector is placed above the stage, to reflect sound more directly rather than diffuse. The back side of the reflector is an absorbing surface as well. Because the panels behind the stage can be flipped to reflect or to absorb sound, a large variety of reverberation can be created between 0,78 and 2,28 seconds.