Engineering an opera house: I L 10431 r) the new Glyndebourne Stas Brzeski Derek Sugden John Thornton John Turzy1 l\.. H'I

sightlines and create the required acoustic; layout of the building is based on circular the fabric must provide good acoustic isola­ forms, which are used to soften its impact on tion; and the ventilation system should be the site. Recognizing that the auditorium and inaudible. Also, theatre and lighting equip­ stage areas have the same requirement for ment have very specific needs. (These are acoustic isolation and generate similar the technical criteria; the architectural plan­ widths, they are contained by an oval-shaped ning, too, has its own demands). massive brick wall, the 'fortress wall', At one Apart from the requirement that only one sea­ end is the auditorium, at the other the back son should be lost during construction, stage, and between lie the side and centre Glyndebourne presented another challenge: stages with the flytower above. how to relate to the House and gardens, and Around the fortress wall is wrapped the an­ maintain those qualities which make cillary accommodation: dressing rooms, 'Glyndebourne' unique. offices, and circulation space. Primary ser­ The concept vice;:; distribution is located in this zone. Whatever success the design has stems from There is a basement. The area behind the the simplicity and clarity of the overall con­ proscenium contains plantrooms, stage 1. Glyndebourne in 1934: Organ Room (left), cept of the building, which works for all dis­ Theatre (right). equipment and dressing rooms, whilst in front ciplines at all levels. The diagram may seem there is a ventilation plenum beneath the obvious but a study of other theatres soon Introduction auditorium, cloakrooms for the public, and reveals that its clarity is exceptional. Such The new Glyndebourne Opera Hou.se opened plant rooms for the front-of-house areas. The on 28 May 1994, the 60th anniversary of its simplicity is not easily achieved and relies on back stage plantrooms supply air to the predecessor, with the same opera, The the complete integration of architectural, auditorium via two huge concrete ducts. Marriage of Figaro. The original building, con­ engineering, and acoustic design. Instead of trying to reduce the impact of the new Opera Noisier plant such as boilers and chillers are structed by Sir John Christie in the grounds House by fragmenting it, like Glyndebourne in a separate refurbished brick out-building. of Glyndebourne House (Fig.1 above) near House itself, the Hopkins' chose to create a Lewes in East Sussex, was not only too small The rehearsal stage too is outside the main single compact building and then reduce its for current demand, but suffered from poor envelope next to the loading bay, in which visual bulk, both by cutting into the hillside acoustics and sightlines, had inadequate another stage can be built if necessary. The and through the detail of the design. ventilation, and sub-standard back stage contours of the site are such that the rehear­ facilities. By 1987 his son, Sir George Christie, The design is a natural consequence of sal stage is almost completely underground, had begun to plan a new Opera House; after choosing a horseshoe-shaped auditorium for revealing its presence only by a low brick wall approaching nine architects and asking two the intimate atmosphere it creates. The whole topped by a band of glazing and a lead roof. to develop proposals, he appointed Michael Hopkins & Partners early in 1989. Arups became involved in all aspects of the engi­ neering and acoustics design apart from Energy centre theatre equipment and production lighting. Fortress wall Bar, shop and box office The brief called for an increase in seats from 830 to 1150 and an improvement in technical Stage and Ambulatories Backstage \J flytower over standards. Sir George Christie was quite 2. clear, however, that music, theatre, and an Concept intimate atmosphere took precedence over diagram. technology. He did not want a building where the technology became an end in itself. Basement - Clarity and integration plant room The design of an opera house is complicated. The problems of long spans over stage areas Rehearsal and the support of balconies and flytower are stage obvious, but there are many more: the form and detail of the auditorium must give good

3. The new Opera House looking westwards toward the South Downs.

3 Bri,ckwork and the fortress wall cities built houses onto the outside of Outside the fortress wall, exposed precast Glyndebourne House is a collection of mellow cathedrals and castles. This structural prin­ slabs with an in situ topping are supported on redbrick and stone buildings with gardens ciple reinforces the architectural concept. precast beams which span between the and lake, set in the Sussex Downs. The new fortress wall and brick piers. The outer ends •The Hopkins' work places great emphasis on Opera House not only had to relate to these of the beams appear through the walls and the honest use of materials, but brickwork in physical characteristics, but also recreate the piers to make the construction legible and large contemporary buildings is normally particular ambience which Glyndebourne add detail lo the brickwork. Brick spandrel has. In part this is created by the setting and relegated lo a cladding skin or a facing for panels span between the piers as flat arches precast units. This Is betrayed in the bonding the tradition of picnicking in evening dress in carrying their self-weight. Precasting was patterns. the use of the bricks in unlikely situ­ the gardens. It also lies, like the picnic, in the chosen both for speed and for quality of contradiction between sophistication and ations. and lt1e location of mastic-filled move­ finish; also, in the case of the accommodation simplicity. In the old Opera House a complex ment joints. These are required by the expan­ structure, its form reflects the use of timber sion of brickwork and the lack of flexibility of art was performed at its highest level in a and cast iron in earlier brick buildings. The building which could best be likened to a modern cement monars as much as by the concrete mix was selected for its light colour need to absorb differential movements be­ large church hall. Some people were con­ and contained a mica-rich sand to give it tween frame and cladding . Nevertheless cerned that its acoustic qualities should not sparkle. Precast panels were also used to such joints would have undermined the visual be lost but these in fact were poor with a dry form the ceiling over the auditorium and integrity ol the load-bearing structure and led sound and noise from aircraft using Gatwick. create the recessed lighting gallery. These to difficulties in detalling. They would also elements play an essential role in the audito­ Early in the design the architects considered have been difficult to locate structurally and using flint walling, a local material. but settled rium acoustics: apart from providing the mass undesirable acoustically, so the older tech­ necessary as part of the double-skinned on brick as more appropriate. The hand­ nology of lime putty mortar. which is more made bricks not only related its construction acoustic enclosure, their sculpted form tolerant of movement. was adopted. The rellects and diffuses sound. to the House, they also introduced a quality other distinguishing feature of modern brick­ and scale of detailing which further reduced work,. bonding patterns resulting from cavity Above the precast units, the primary roof its impact and recreated the simplicity of the construction, was avoided by building solid. structure consists of radial steel trusses old building. cantilevering into the centre from the peri­ Auditorium, ancillary meter where they are supported on the The fortress wall required mass to achieve its accommodation and roofs acoustic performance and, apart from under balcony columns and tied-down by the fort­ Within the auditorium the balcony structures ress wall. Above the trusses are double­ the flytower, the vertical loads are not particu­ are of exposed precast concrete units larly high, since above basement level the skinned, lead-covered plywood panels. The stitched together by an in situ spine beam, mass of the lead and build-up of the panels is building consists of single-storey spaces with balanced on a ring of columns. and re­ long-span roofs. or three-storey accommoda­ used for acoustic insulation. The trusses for strained at the back by the fortress wall. (This the back stage are also radial, but in this tion. This led to the idea of constructing the follows the same structural principles as the fortress wall out of load-bearing brickwork, case the centre of the system lies on the back Mound Stand and Compton and Edrich Stands wall of the flytower rather than over the space. double-skinned around the auditorium itself at Lord's.) for acoustic isolation. It was then logical to Continued on p.9 add the enclosing accommodation as a The exposed thermal mass helps to smooth dependent structure, in the way mediaeval temperature fluctuations in the auditorium. 5. Main entrance (Organ Room in Glyndebourne 1J1o House is on the left).

Bricks and mortar

The bricks had to be similar to those employed at Glyndebourne for its An arch was constructed at CERAM's used in Glyndebourne House. as well good water-retention properties, laboratories using the chosen bricks as satisfying engineering require­ workability and availability. It is pro­ and lime putty mortar in the agreed ments, and their selection involved duced by hydrating or slaking the bonding pattern. The arch was but­ considerable research. The final lime (calcium oxide) with water to tressed in a similar manner to those choice was a Selborne hand-made, produce calcium hydroxide. The on the building, and was loaded in a re-pressed brick. made from gault reaction is exothermic, vigorous and predetermined sequence. Strains clay extracted from a deposit mined potentially dangerous. The putty is and movements were monitored at for many years. They are a modified stored under water, the longer the relevant points such as springing imperial size, 220 x 106 x 60mm, to better, for increased plasticity and point, extrados centreline and intra­ match those in the walls of the bonding properties. dos centreline. The arch withstood House . Compressive strength is Modern cementitious mortars (which the applied load without undue dis­ 2 27.5N/mm with an irreversible mois­ incorporate unhydrated dry lime) set tress and with displacements close ture movement of 0.37mm/m - by the action of hydration with 11J ater. to predicted values . classified as low by CERAM Building The mortar sets throughout the depth Bricklaying commen ced with the con­ The maximum len gth of continuous Technology. Water absorption is of the joint and, like most cement­ struction of sample panels for the brickwork on th e buil ding is just 143%. based compounds, is accompanied approval of bricks, joint profi le, under 1O Om aroun d the front of the The facing bricks have a textured by shrinkage. blending and co lour. This was a use­ Opera House. In other areas, per­ surface produced by coating with In contrast. true lime mortars set by fu l testing ground to estab li sh work­ forations in walls for doors or other sand before firing. Both these and the action of carbonation at the ing procedures for the main building. opening s reduce d this length . The the common bricks are made of the exposed surfaces of a join t. Atmos­ The cross-bonded flat brick arches potential long term irreversi ble mois­ same clay and have the same pheric carbon dioxide is absorbed span up to 2.9m between skew­ ture expansion of the bricks has been mechanical properties, thus avoiding into the mortar and the calcium backs built into the pi ers. They are estimated as about 24mm . whi ch problems of differential movement hydroxide present is converted back 334mm th ick and 536mm high, are does not accoun t for moisture move­ between facings and commons to calcium carbonate in a lengthy unreinforced . and inco rporate a rise ment wh ich occur.rnd over the bonded together or in adjacent process known as induration. The of 25mm. They support the ir own months the bricks were stockpiled in leaves of cavity walls. depth of setting is relatively shallow, weight and a brick spandrel panel the open Thi s strain was considered acceptable. taking into account the Knowledge about the manufacture. and the core of a mortar joint remains above . The bri cks for each arch were restraint that was pro vi ded by the use and behaviour of lime mortar. plastic. It is this softness that permits made from a single column of clay. floor slabs and beams. chosen to avoid the need for move­ the masonry to absorb stresses Each brick had a unique numbe r. ment joints. is not widespread. and caused by movement. Any cracking and complete arches we re delivered The us e cri load-bearing brickwork an investigation was carried out. that does occur is small and dis­ on a single pallet. t11th lime putty mortar on a buil ding including a visit to The Lime Centre in tributed along and across a wall . In Although the arches are relati ve ly of this sc ale has not been seen for Hampshire to gain practical experi­ effect. movement joints are created lightly stressed there was concern many years. The investigati ons. tests. ence. Lime for mortar is produced by ;:it P.very bed and perpend joint tha t th ey might be prone to move­ and trial s we re an essential part of burning chalk or limestone (calcium The lime putty was delivered in tubs. ment and, with negl igible tensi le developing the design and under­ carbonate) in a kiln at about 900'C to and the mortar mi xed on site using strength , exhibit unwanted crack ing standing the techniques required for produce calcium oxide. Two types of gauging boxes and mortar mixers: A load test was carri ed out. both to con structi on In th e end . though , the lime are used for mortar: lime putty or the proportions were 1 2:9 (white PC : answer this question and to assess oes1q n depends on enqineerinq d1y hyLlrale. The former was lime putty : sand). the comparatively weak mortar judgement

THE AAUP JOURNAL 3/1994

- J5rTUWi 4 - =:

The acoustic

The brief Design and analysis: Sir George Christie's brief was simple the 1:50 scale model and direct, but very difficult to As the design developed, it became achieve: he asked for a sound which clear that Hopkins' auditorium would combined the clarity of the old house not include any 'carpets and curtains· with a 'resonance· that would flatter and a minimum of absorbent the orchestra and singers. Like many secondary fixings, so the volume per acoustic briefs it illuminated two seat could be relaxed a little. fundamental criteria which are However, the Bm3 per seat did virtually mutually exclusive. Through­ decrease to just below 7m3 per seat out the history of opera there has as expected, indicating a mid­ 6. Acoustic scale model showing frequency reverberation time of 1.4 been an argument about whether convex reflectors installed for impulse testing . words or music are of primary impor­ secs. Anthony Whitworth-Jones, the tance; the French with their literary General Director of Glyndebourne, 7. Auditorium roof showing use of structural ribs for sound placed great emphasis on clarity. He tradition favoured the words, whilst diffusion and 'jelly-mould' sound diffusing form of vertical precast sections. the Italians were more concerned considered the Coliseum in London with melody, harmony and timbre. and the Bayreuth Festspielhaus with RTs of 1.5-1.6 secs to be too rever­ This dichotomy is still with us today beran t. Both these auditoria, but and its resolution, achieving that particularly the Coliseum, lack short delicate balance between words and powerful side reflections. With the music, was the starting point for the short powerful side reflection, an RT geometry of the Opera House as a of 1.4 secs - still somewhat more response to Sir George's brief. reverberant than most opera houses Setting the standards - was considered to be appropriate. At the earliest stage, after the With the geometry and seating Hopkins' appointment but before that finalized, a 1:50 scale model was of the theatre consultant, some dis­ constructed in Arups' Model Shop, cussions took place whilst the with the first roof and ceiling scheme. auditorium still had the vestigial fan­ shaped form of the John Bury brief*. Four were tested before the archi­ tects were convinced about a design. This did not inhibit the setting of which incorporated a 'flat dome', a geometrical standards to achieve the common feature of many opera preferred acoustic. Auditoria for houses. Sound waves focus in a music, whether concert halls or opera similar way to light, and this design houses, invariably fall short of the avoided the focusing problems asso­ volume per seat necessary to ciated with many earlier schemes. achieve the appropriate reverbera­ The model was also essential in tion time (RT); defined as the time exposing focusing from the drum at taken for a sound to decay through high level. This was corrected by the 60dB, RT is still considered the prime introduction of convex panels. Slottec criterion for measuring the quality of lift-off panels were also introduced to sound within an enclosed space. Its allow the inclusion of small areas of value at different frequencies is also absorption to deal with certain focus­ very important to the quality of the ing and to allow for a limited degree sound. It is directly proportional to of fine tuning. volume and inversely proportional to the absorption of all the surfaces. Extensive work was carried out in the model to define the final geometry of Volume decreases as the architec­ the balcony fronts - fundamental in tural concept is developed and achieving, after the direct sound, the detaile.d!-ln addition, clients and strong early reflections which provide architeCfS-linLi ways of increasing intimacy, clarity and envelopment. seat numbers as the design and The detailed geometry was resolved sight-line analysis develops. in the model to achieve this without Initially, Bm3 per seat was the volume focusing effects. The profiles reflect fixed to achieve the preferred RT; for sound down into the stalls at the clarity, a maximum 17-1 Bm between sides, with a subtle change in profile balconies was set to ensure strong towards the back of the auditorium. early side reflections; whilst for and are slotted to provide acoustic acoustic and visual intimacy, the transparency where focusing would furthest seat was to be a maximum of occur. 30m from the stage riser. To ensure an orchestral sound of 8. Derek Sugden firing a .38 revolver The quality of any acoustic is during initial acoustic tests in December 1993. some richness and warmth. a 20- immeasurably enhanced by a quiet 25% increase in RT at low frequen­ background. To achieve this a cies is needed. This is quite un­ double skin wall and roof construc­ common in most opera houses, tion of sufficient mass with the where orchestras sound dry and appropriate cavity was specified. rather 'boxy·. It was most rewarding together with an air-conditioning tl'iat Hopkins design of the audito­ strategy lhat wou ld ensure a back­ rium without an architecture of ground noise level of PNC 15 - second and third fixings was funda­ approximating to the threshold oi mental to achieving this aim. The hearing , soffits are of exposed concrete. the

6 THE ARUP JOURNAL 3/1 99•1 main floor 1s a stiff composite layer tural scheme. together wilh lhe aban­ with a minimum thickness of 40mm. donment of a proposal for sliding and all the balcony fronts are of very proscenium boxes and subsequent rigid solid pine. with a geometry that change in geometry of the sliding adds to their structural stiffness and bridges - part of the original John so ensures a minimum of bass­ Bury brief - resulted in a decrease absorb1ng resonance. This was a to the overall length of the pit. To most important aspect of the acoustic compensate for this. the distance design. between the orchestra rail and stage There was extensive acoustic input riser was increased to 4m. into the seat design in addition to the Following the lest concert. the close work with the mechanical London Philharmonic Orchestra. with engineers to achieve the specified c.75 players on modern instruments. noise attenuation. The seats were tesled various configurations of the tested in a laboratory with and with­ orchestra for Figaro and Peter out auditors. Following the first test. Grimes, under conductors Bernard adjustments were made to certain Hailink and Andrew Davis. The rostra aspects of their construction to geometry, particularly al the back of achieve the specified absorption the pit, was resolved both for sight coefficients. These modifications lines and comfortable seating . were confirmed in a final test. The other Glyndebourne band is the Predictions and Orchestra of the Age of Enlighten­ measurements ment. about 50-strong, who play on Measurements in the model pre­ ·original, and thus less powerful. dicted a mid-frequency RT of 1.4 instruments. In view of this. it was secs, with 1. 7 secs at 125Hz. A test desirable that all their players should concert with full audience was held sit forward of the stage riser, but with on 28 March 1994, where measure­ the growing demand of orchestral ments gave an average mid-fre­ players for increased space and the quency reverberation time of 1.25 presence of the safety net this was secs with 1.65 secs at 125Hz. The not possible. However, with the clarity index was high throughout the adjustable pit lift slightly below the auditorium and the impulse traces preferred stalls level the OAE can be were of 'text book' shape. accommodated with the brass and The orchestra pit woodwind placed under the safety 9. The auditorium. One of the central problems for an net or edge of the cantilever. acoustician in the design of an opera Coda - art or science house is the balance between pit and Acoustics is often referred to as a stage sound . The orchestra pit of a 'black art', but it is no more nor less 10. Semi-circular backstage area. modern opera house must be able to an 'art' than any other branch of engi­ house and adapt to a wide repertoire, neering. Engineers , like architects. from the orchestras of the Renais­ work from precedent. but primarily sance operas of Monteverdi and from intuition. using calculations as a Cavalli, through Haydn and Mozart. guide to what they want to do, and to Verdi, Wagner and Richard with detailed analysis as a supporting Strauss, and on to Birtwistle and tool. Acoustics does perhaps differ, beyond. in that the choice of an acoustic is In the last 200 years the orchestra highly subjective. whereas the overall has changed out of all recognition stability of a structure is not a matter and the instruments have become of taste or opinion. A quiet back­ enormously powerful:J;;onr 1ctors ground, however - one of the most have a love affair with that great lush important qualities of a great acoustic sound favoured by many recording - is not a matter of opinion, although engineers and producers . The power even on this subject we can argue of the human voice may have how quiet we should make an increased somewhat. but there is no auditorium. This aspect of acoustics, comparison with the size and power the setting and achievement of sound of a modern orchestra. insulation and sound attenuation, was one of the great success stories at The brief for the orchestra pit was not Glyndebourne. Rob Harris of Arup precise about the maximum number Acoustics observed that it was the of players. There is a tradition at first auditorium we have measured Glyndebourne which encourages that achieved PNC 15 at the first test young singers, and to achieve the with no modifications or 'tinkering ' delicate balance between stage necessary sound and pit sound with a large modern orchestra, a maximum dis­ tance of 3.6m between the orchestra • John Bury was the theatre designer and consul tant who prepared th e dra wings lor rail and the stage riser was agreed . It the compet1t1on brief. He had designed a was always the intention to place the se ri es ol Glyndebourne productions lor more powerful instruments of a Pe ter Hall. inc ludin g Figaro. Fide/10. and modern orchestra on descending Ca rmen. and had been auditorium rostra under a limited cantilever consultant to the or1g1na l Edinburgh section of the stage. The final struc- Opera House.

THE AAUP JOURNAL l \')~H .,. Conunuea lrom page .J · Primary truss The trusses span from the fortress wall to a sem1c1rcular torsion beam hung from the fly­ Roof slab/table top iower roof. the semicircle being used to Steel leg/ create a skylight. The side stage roof trusses tubular co lumn simply span from flytower to fortress wall. --+--- Hangers In these areas the acoustic requirements are less than over the auditorium so lhe ply and f Wind posts lead roof is the only skin. thus allnw1no lhe Outli ne of steelwork to be seen from below The roof of auditorium roof the rehearsal stage also consists of exposed . -. Steel plate steelwork with lead/ply panels. Like other shear wall parts of the design the steelwork continues Side stage girders the contrast of simplicity and sophistication. the design being based on simple back·to­ ''· back angles and tie rods. The sophistication Proscenium arch lies in the organization and the refinement of --. t11e details. The roof over the accommodation uses timber and steel flitch beams to intro­ Concrete leg/ duce a more domestic scale. shear wal l The exposed brick, the finely detailed precast concrete, the reclaimed pitch pine balcony fronts and panelling, and the bare timber floors have a tactile quality which creates a particularly restful atmosphere in the audi­ torium. This is enhanced by the apparent absence of services. not easily achieved in a building without applied finishes. Air is sup­ plied through perforated seat pedestals, lighting is recessed into the precast concrete, and conduits are cast-in. The back-of-house Side stage areas were detailed with the same attention; great care was taken over the co-ordination of services, brickwork and concrete, conduits were cast-in wherever possible and final routing was simple. A fairly robust approach was adopted for the actual detailing and selection of fittings. 14. Flytower structure Flytower The largest single piece of structure and the most conspicuous element of the building ls Construction Timetable Construction started in March 1991 with an lhe llytower. its size following 1nevllably lrom Architectural appointment: February 1989 that of the stage and the height of the pros­ enabling works contract to divert existing site cenium. Originally it was to be elliptrcal and of services. After the close of the 1991 season Scheme design approval: December 1990 brick construction. but as the design de­ work began in earnest with the demolition of Start on site (Phase 1A) 27 July 1991 veloped the shape changed to a rectangle as much as possible of the existing building with curved front and back walls. As well as. without affecting the operation of the main Start on site (Phase 18): 5 August 1992 softening the shape, the curves create part of the opera house in the 1992 season. Completion and handover: 31 December 1993 spaces for the curtains. a staircase, smoke Work then proceeded on the structure behind extract plant, and dimmer rooms. However, the proscenium until after the 1993 season First night: 28 May 1994 the curved torsion beams required to support when the rest of the old opera house was these walls were very large and would have demolished. Credits been an unacceptable intrusion into the Client: Before work started there had been concern Glyndebourne Productions Ltd auditorium above the proscenium. The de­ over the problem of removing 33 370m3 of sign was changed so that the walls were sus­ Architect· excavated chalk through the narrow country Michael Hopkins & Partners pended from roof top trusses. which also lanes. This was solved by a slight modifica­ helped speed construction. A grlllage of ex­ Consulting engineers: tion to the topography of one of th e adjacent Ove Arup and Partners Jeremy Bras1ng1on Poi C:u·;.rv posed steel trusses is earned by four steel fields. The Christies seemed to delight in the Barney Jordan Rob Kinch. Clare Murohy Steve Peel columns suppc.. ted on concrete shear walls. Caroline Ray Mervyn Rodrigues Davia D Sm11h John T/1orn1on 10m deep hole. literally outside th;:,1r back Jolin fuflynski (structural) two of which form the proscenium. The grid door. as a sign that th eir project was under floor and stage equipment are suspended John Berry Stas Brzcski Manin Grcennlal Caroiyn

THE AAUP JOURNAL I 1; I 9 Auditorium Early on, modelling studies were carried out in conjunction with Cam­ ventilation system bridge University's Department of Theoretical Physics and Applied Choice of system Mathematics. A 1:25 perspex model Fly tower The design of the ventilation system of the auditorium, stage alid flytower for an auditorium is distinguished by was inverted in a water bath, with two key features: the large concen­ coloured saline solutions of various 12. tration of occupants within a relatively densities used to represent hot air Aud itorium small proportion of the overall ventilal1on movement. The choice of a displace­ princi ples. volume, and the absolute importance ment ventilation system was con­ of the system's acoustic performance. Return air firmed and important data obtained ductwork riser The decision to ventilate the audito­ for subsequent use in the design. t Stage rium by a displacement system sup­ System design plying air at low level under the seats To meet the PNC 15 noise limit, plant and extracting at high level was is located at a distance from the natural and intuitive. Systems supply­ auditorium and, in addition to exten­ ing air from above must overcome sive attenuation, very low air velo­ the natural upward airflow resulting cities have been used in all dis­ from buoyancy forces generated by tribution systems to avoid noise were imposed : the ability to allow Temperatures were recorded at vari­ the heat of the audience. Falling fresh generation. The ventilation system is seats to be removed to locate ous locations and tracing smoke air becomes mixed with rising hot air integrated with the building fabric cameras for video broadcasts. and used to examine the flow of air so that heat and odours are recircu­ wherever possible. Four 50m long, the resilience of the performance of throughout the auditorium and stage lated to the occupants. In contrast, 2m x 2m concrete ducts buried in the the outlet to the Glyndebourne tradi­ area . The results showed an accept­ displacement ventilation comple­ ground beneath the backstage areas tion of placing coats under seats. able correlation with the predictions ments the natural air flow pattern. connect the ventilation plant to the On completion of the tests and stud­ of the earlier scale model test. Cooler, fresh air supplied from below auditorium. Air is injected into large ies, the integrated seat pedestal air The real proof came with the first use replaces stale rising air so that the plena beneath the floors of the stalls outlet was chosen. A detailed simu­ of the auditorium for a public perfor­ occupied zone is constantly purged and each of the circles, and enters lated load test at an acoustic labora­ mance, at the 28 March 1994 test with conditioned air and local re­ the auditorium through air supply out­ tory followed. A block of 24 seats with concert, which lasted approximately cycling is eliminated. There is no lets integrated with the seating sup­ air supply pedestals was built above 90 mins. Temperature measurements need for higher air velocities to over­ port pedestal. The orchestra pit is a plenum pressurized by a fan . A compared favourably with the design come the natural air movement, so similarly supplied, but with a flat grille lamp bulb was placed on each seat predictions and reports from there is less likelihood that noise will served by a separate plenum con­ to represent the heat generated by members of the audience and result. A benefit of the resulting nected to a branch of the main sys­ the audience, and detailed air tem­ orchestra were positive. The acoustic increased cooling efficiency is that tem. The exposed structural concrete perature and velocity measurements performance of the system has been air is supplied at higher temperatures within the auditorium provides a sub­ were taken, as well as further confirmed both by measurement and than required for ceiling supply stantial thermal cooling store which acoustic measurements. by its inaudibility to the human ear. systems, so refrigeration running smooths temperature swings by costs are reduced. System tests Conclusion absorbing and releasing heat energy. The heat load test was repeated on Tes ting at successive stages in the 11 . Seating with acoustic absorbent Choice of air outlet site at full scale during commission­ design, construction, and commis­ base, mounted on integrated Various auditorium air outlet types ing trials. Lamp bulbs and convector sioning process underpinned initial air supply pedestal. were considered, both integrated heaters were distributed throughout design assumptions , confirmed detail with the seat support and separate. the auditorium to simulate the heat design parameters and , finally . Each outlet was tested to prove its air generated by a full house - equiva­ proved satisfactory system perform­ flow and acoustic characteristics and lent to about 1250 domestic 1DOW ance. The successful outcome con ­ examined to ensure that it could be lamps Sufficient theatrical lights firms the importance of testing in accommodated within the space were rigged and operational to repre­ situations where attention to detail is available. More unusually, two further sent the heat given off by production paramount in achieving the end criteria peculiar to Glyndebourne lighting during a performance. result.

13. Fabric canopy, designed by Arups, over the foyer entrance

8 THE ARUP JOURNAL JI 1994