The new Central Library in Minneapolis fills a downtown city block with an iconic space for learning. The library is comprised of two buildings that are separated by a soaring space known as Library Hall. This mass is made welcoming by a glass exterior and a multi-storey, light-filled atrium that cuts through its center. Kirkegaard influenced the shape and finishes of the atrium to control the buildup of sound. To control excessive background noise in Library Hall Kirkegaard helped to integrate absorptive material into the atrium ceiling. This grand space provided a beautifully supportive acoustic environment for staff and guests alike.
Kirkegaard also made recommendations for the stacks, meeting rooms, and other public spaces to control background noise and improve speech clarity. Equal care was taken with the doors and partitions at the music practice rooms, which are detailed to reduce sound transfer between the rooms and into the stacks. To keep the stacks appropriately quiet, absorptive material, wrapped in Mylar, was installed out of sight on the top of the book stacks. To allow ultimate flexibility throughout the north half of the building, there is no exposed ductwork. Instead, air is supplied through an under floor plenum. Patrons walk on precast concrete panels supported by a forest of short columns that rest in turn on a heavy concrete structural slab. Such a system is inherently quiet and provides excellent acoustic isolation from floor to floor.
Particular attention was paid to a 243-seat auditorium with full audio and video presentation capabilities. The auditorium has become a favorite site for public hearings and community events.