Introduction
This paper describes the acoustic design of the new Lyric Theatre in the Lowry, Salford. It outlines the key acoustic design parameters and describes the integration of the architectural aesthetic with the acoustic requirements. The building will open on 28th April 2000.
The Lowry
The Lowry will accommodate facilities for both visual and performing arts in an exciting, stimulating venue for education and recreation. Bordered by the Manchester Ship Canal and facing a new triangular public plaza it will be the landmark focus of the redevelopment of Salford Quays. The Plaza will be a sheltered and lively venue for community activity, gathering together three primary approaches to the Centre, including the terminus of the new Metrolink light rapid transit system. A commercial development will enclose the remaining sides of the Plaza, and waterside promenades provide pedestrian routes from the building entrance to the Quayside.
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View of the Lowry from outside ( Credit Duffie White )
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The Lowry contains a 1730 seat Lyric Theatre, a 466 seat Adaptable Theatre
with shared rehearsal and dressing facilities, Art Galleries to display
the City's collection of L.S. Lowry paintings as well as changing exhibitions,
artworks, an interactive gallery covering the creativity of the arts, together
with bars, café and waterfront restaurant.
The Adaptable Theatre, on an axis aligned with the Lyric Theatre, has a courtyard form to suit various performance arrangements and a curved enclosing foyer with dramatic views across the ship canal. Rehearsal space is provided above the Adaptable Theatre, with the administrative offices located at ground level.
The Lyric Theatre forms the heart of the building with stairs and balconies providing direct access to three auditorium seating levels. A perspective view of the Theatre is shown in photograph 2.
Acoustic Design of the Lyric Theatre
The Design Team's starting point for the development of the Lyric theatre was a study of the Edinburgh Festival Theatre which has a similar layout and seating capacity. It also stages similar events and has a reputation for excellent acoustics (1). Other comparable theatres visited included Glyndebourne (1250 seats); the Theatre Royal, Glasgow (1566 seats); and the Grand Theatre, Leeds (1603 seats).
Client Requirements
The Lyric Theatre is intended to be a multi-purpose auditorium so as to serve a wide variety of needs. The Operational Report and Business Plan (2) proposes that key aspects of the programme for the Lyric Theatre should include the country's finest opera, ballet, dance and drama touring companies. Examples of companies envisaged include the Birmingham Royal Ballet, English National Opera, Northern Ballet Theatre, Royal National Theatre, Royal Shakespeare Company, Welsh National Opera, Glyndebourne Touring Opera and D'Oyly Carte. The programme also includes children's shows, individual artists and commercial shows.
The Operational Report and Business Plan requires the acoustic of the auditorium to be suited to a wide range of uses. The report identifies that for this to be made possible the acoustic will need to be variable.
Variable Reverberation Time
Analysis of the projected uses of the Lyric Theatre, in terms of their duration over a typical year, and in terms of generally accepted RTs of auditoria for different uses, revealed that two acoustic conditions would be needed (3), (4). One condition is where the RT would be around 1.3 seconds, (suitable for opera etc.) and one where a shorter RT of around 1 second would be more appropriate (for speech). The acoustic design of the Lyric Theatre therefore makes provision for the variation of the reverberation time.
The change in RT is achieved by the deployment or retraction of 600 m2 of absorption in the form of curtains above the acoustically transparent ceiling line. The curtains are located on 6 separate tracks and are electrically operated. Curtain boxes are provided so that when retracted, no curtain area is left exposed to the theatre.
Auditorium Ceiling
Like other modern and well equipped theatres, The Lyric Theatre of the Lowry is a complex technical space where the integration of many requirements is essential. For example the architecture and aesthetic requirements must be co-ordinated with stage lighting, effects lighting, environmental comfort and of course the acoustic considerations.
The Lyric ceiling plays a key role in the integration of these requirements. It is particularly important in achieving the acoustic requirements specified in the client's brief and in delivering the architect's concept and intimacy for the space.
The ceiling is a suspended perforated metal and mesh surface above the seating which is intended to provide a visual, but not an acoustic, barrier which hides the technological necessities of the theatre that are situated above it. It is a complex shape comprising many over-lapping 'petals' each of which is designed to be a flat surface. A lighting arrangement between the petals washes light across their surfaces, the result of which would be to make these acoustically transparent surfaces appear solid when lit. An orthogonal wire mesh in the central area towards the proscenium is intended to provide a visual screen that would hide the lighting bridges above when light is shone across its surface. An area of the ceiling towards the back of the theatre is hinged to allow it to be raised to allow the follow spot above the ceiling surface to light the stage.
The percentage open area of the petals was of particular concern and we tested perforated metals sheets having varying degrees of openness (5) to see how they would behave in the frequency range of interest. For the reasons already mentioned the architect was keen to use panels having the lowest percentage open area compatible with the acoustic requirements.
Eventually we agreed that a perforated metal having an open area of 36% would be acceptable. However, the open area of the ceiling as a whole, i.e. that of the perforated metal petals and the mesh, would be substantially greater.
The large quantity of metal forming the ceiling gave
concern over the possibility of rattling and resonances
in the petals, mesh, support structure and interfaces. The contractor has
been made responsible
for ensuring that the ceiling does not rattle or produce
any attention catching noise. To assist in achieving this, there should
be no metal to
metal contact – neoprene rubber forms a boundary layer.
To allay concerns over rattling even further, full size mock-ups of each element have been built and tested together with the support structure.
Reflectors
The architectural 'cheeks' on either side of the proscenium have been designed to maximise early reflections. The 'cheeks' are convex and extend full height.
Acoustic reflectors are also provided on the underside of the lighting bridges and above the forestage. These are all above the mesh and perforated metal ceiling and the intention is that they should not be visible from the seating area.
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The Lyric Theatre
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Orchestra Pit
Particular consideration has been given to the orchestra pit to ensure that excellent conditions are provided for the orchestra. The pit can be varied in size by the use of two elevators. At its maximum it will accommodate up to 90 musicians. Low frequency absorption is provided in the pit to control resonances, and the pit overhang is relatively small, being just 3m.
Mechanical Services
The background noise criterion for the theatre has been set at NR20. The mechanical services design employs a combination of underseat pedestal diffusers together with low velocity diffusers on the step risers. Extract is provided through the 'crinkle' wall above the visual ceiling line.
The main supply plant for the theatre is located on the top floor of the adjacent tower building, and is ducted through very large builders work shafts into the underseat plenums. Extract plant is located at high level to the sides of the theatre and ducted behind the 'crinkle' wall.
Smoke extract is provided by a ducted mechanical extract system attenuated to maintain the sound insulation of the fly tower.
Sound Insulation
The current external noise environment is not excessively high, but the site is on a flight path. The predicted peak traffic flows on the new roads along the quayside are quite high and ships do occasionally use the adjacent canal.
The shell to the theatre is primarily 200mm thick reinforced concrete. Around the theatre are buffer zones comprising quiet areas (such as storage rooms). Door lobbies to circulation areas are provided to maintain the sound insulation. The roof to the theatre is concrete with a heavy plasterboard skin supported off the bottom of the roof trusses.
The Lyric theatre is separated from the Adaptable Theatre by two sets of large 55 dB doors either side of a shared scenery store. There is a structural movement joint in the floors and walls separating the two sides of the building. The level of sound insulation provided between the two theatres will allow for the simultaneous use of both with no disturbance in either.
References
(1) L G HASLAM, The Acoustic Design of the Edinburgh Festival Theatre, ProcIOA, Vol 17, Part 1, (1995).
(2) Operational Report and Business Plant for the Lowry Centre, January, 1996.
(3) M BARON, Auditorium Acoustics and Architectural Design,
E & FN Spon, London (1993)
(4) L BERANEK, Concert and Opera Halls: How they Sound, Acoustical Society of American, New York, (1996).
(5) Acoustical Uses for Perforated Metals, Industrial Perforators Association Inc.
Acknowledgements
The authors would like to thank the architects, Michael Wilford and Partners, for their help and information used to prepare this paper. Thanks are also due to Alex Burd for his guidance and help throughout the development of the acoustic design.
The authors are acoustic consultants with Sandy Brown Associates, 1 Coleridge Gardens, London NW6 3QH, UK, and 16 West Terrace, South Queensferry, EH30 9LL. Sandy Brown Associates, members of the Association of Noise Consultants.
This is a revised version of a paper they gave at the IOA Conference in Manchester in October 1999.
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