Birmingham Hippodrome 2000, Acoustic design of the new theatre, dance studio and refurbished auditorium Ian Knowles FIOA and Kyri Kyriakides FIOA.

External view of the Birmingham Hippodrome. The Birmingham Hippodrome was built in 1899 and has since been at the heart of Birmingham's cultural life. It has been the home to the Birmingham Royal Ballet since 1990 and Dance X change (the National Dance Agency for Birmingham and the Midlands) since 1994. A £20 million National Lottery Grant through the Arts Council has created Britain's first Centre for the treatment and research of Dance Injuries, a 200 seat studio theatre, provided dedicated dance studios for the Birmingham Royal Ballet and Dance X change, refurbished the original auditorium and provided new foyers and a new entrance. The Lottery award was supported by a further £2 million from the European Regional Development Fund and Birmingham City Council who restructured the lease arrangements to secure the Hippodromes future for the next 125 years. The £2 million matching funding was by public donation and sponsorship. Internal view of the auditorium from the main stage. Sound insulation Planning The new Studio Theatre (named the Patrick Centre) and dance studios are located in a new building, and are built on the site of an old nightclub adjacent to the Hippodrome. It is important to realise that in the new building, separate companies will be rehearsing or performing, and management controls on sound levels or activities would not be desirable. The constrained site layout has led to the vertical stacking of the studios and the theatre. This has inevitably resulted in onerous sound insulation issues. The main issues involve the effective isolation of the new Studio Theatre from impact sources from the dance studios and dance injuries centre above and the simultaneous use of all the dance studios with little or no disturbance in any adjacent spaces. Internal view of the stage from the auditorium. Strategy The original sound insulation strategy was to provide separate concrete boxes for the individual spaces within the concrete frame of the new building. All of the spaces were initially resiliently supported. During a value engineering process, the dance studios were graded in terms of likely operational sound levels. The Royal Ballet studios primarily use a piano as the music source for their rehearsals, whilst Dance X change use high levels of amplified pop/rock music with occasional live bands. It was decided to apply the maximum protection to the small Dance X change studio, allowing this studio to have the most flexibility (and to be the noisiest). This studio is a completely isolated structure. The large Dance X change studio had its 'lid' omitted, thereby placing some limitation on sound levels, due to flanking through the common roof slab to other areas of the building. The Royal Ballet studio did not include any special airborne sound insulation measures other than a floating concrete floor. Airborne sound insulation was provided by the single dense concrete blockwork wall defining the space. All studios have a 150 mm thick floating concrete floor supported on resilient bearings with a traditional sprung timber dance floor on top. Plan view of the centre. Section through the auditorium. Structure Patrick Centre The section indicates the principles of the acoustic separation of the new theatre within the building. Of particular interest are the inter-laced up-stand and down-stand beams supporting the concrete lid to the Patrick Centre and the concrete floor to the centre for dance injuries above. This design allowed for total physical separation between the two spaces, thereby preventing the transmission of structure-borne impacts from the Centre for Dance injuries above to the theatre. The blockwork walls to the theatre are supported on resilient bearings, as is the concrete floor. Dance X change studios The Dance X change studios comprise a resiliently supported concrete floor with resiliently supported dense blockwork walls. In the small studio, a resiliently supported laminated plasterboard lid is provided. Birmingham Royal Ballet (BRB) studio The BRB studio comprises dense blockwork walls built of the structural building frame. The floor is a resiliently supported floating concrete slab. Auditorium It was a requirement of the Brief that 'any work which is to be carried out in the existing 1887 seat theatre does not compromise its good acoustic qualities.' The Brief required the entire circle comprising 1,018 seats to be re-seated. This resulted in the re-carpeting and re-flooring of some areas. The whole auditorium was redecorated, and the control room re-sited. Acoustic tests were undertaken in the theatre before commencement of the work to quantify the acoustic properties of the auditorium. The acoustic properties of the seats were also quantified and the data was used to specify the performance of the replacement seats. The Patrick Centre auditorium viewed from the stage. Restaurant The restaurant provided an unusual sound insulation issue; it is located on the first floor and open to the ground floor foyer through large slots cut into the perimeter of the floor slab. It was the client's wish that noise from the foyer would not become a problem within the restaurant, but that it would enhance its atmosphere by providing a 'buzz'. Clearly by glazing these areas, a high level of sound insulation could be provided, but this would acoustically separate the spaces too much. It was therefore recommended to include absorption on the slab edge and on the vertical wall opposite, thereby providing some attenuation between the two spaces. Reverberant sound levels were also controlled in both the foyer and restaurant by the installation of areas of absorbent ceiling. The outcome of this element has proved to be satisfactory for both spaces involved. Acoustic cavities The construction of the floating studios and the Patrick Centre was slow, painstaking and frustrating both from the design team and contractor's point of view. The construction of these sensitive and critical elements was programmed to be completed before the building was watertight. Unfortunately, construction of these areas coincided with the wettest winter for many years in Birmingham. Cavities that had to be kept clear of rigid debris between fixed and 'floating' structures ranged from 50 to 500 mm wide. In certain cases, it was easier to fill the cavities with mineral fibre before forming the cavity wall, thereby making it impossible for debris to bridge the cavity. In larger cavities, cleanliness was achieved on a lift by lift basis, protecting the cavity as construction progressed. For the largest cavities, it was possible for workmen to enter the cavities and remove debris once the walls were complete. Dance X change. Patrick Centre finishes The acoustic design of the Patrick Centre required the room to be suitable for amplified music and speech. This condition had to be met with the retractable seating both extended and occupied, and retracted. The target reverberation time for the auditorium was less than one second. Absorbent wall and ceiling finishes, typically 100 mm thick were designed to provide an RT of about 0.7 seconds in both seating configurations. The bass rise was controlled making the space suitable for the performance of amplified music. Dance studio finishes Absorbent wall and suspended perforated ceiling panels were designed for the dance studios. The performance of the suspended panels is surprisingly good, as the mineral fibre is open to the space on both of its surfaces. Nevertheless, these spaces remained quite lively as they have mirrors on nearly half the wall area, with full height windows at one end to the room, and a wooden floor. An RT of about 1.5 seconds was achieved. Acknowledgements The authors are acoustic consultants with Sandy Brown Associates, 1 Coleridge Gardens, London NW6 3QH, UK. The authors would like to thank the joint project architects Law Dunbar-Nasmith and Associated Architects. Thanks are also due to the Birmingham Hippodrome for allowing us to publish this article.