32 Studios for sound and vision CI/SfB 528 Uniclass D527 UDC727.94
David Binns David Binns is the senior partner of Sandy Brown Associates, architects and acoustic consultants
KEY POINTS: Avoidance of extraneous sound is essential Production staff need both full observation and easy access to the studio floor
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Contents 1 Introduction 2 Studio types 3 Planning 4 Services 5 Acoustics 6 Statutory requirements
1 INTRODUCTION 1.01 Scope A TV studio is an area in which activities are performed specifically for observation. (Television cameras are also used outside studios for surveillance in stores, banks and so on.) A sound studio may be used for live broadcasts such as news bulletins, but is most likely to be required for making recordings. 1.02 Broadcasting studios The greatest differences between studios will be in the ancillary areas rather than the studio per se. These differences reflect the nature and attitudes of the client: the BBC in the UK, for instance, is a public service organisation whereas the independent companies are not (although they must adhere to standards set by the Independent Broadcasting Authority). 1.03 Independent and educational studios There are now many small independent studios, operating for private commercial use, for making programmes under contract, and for making educational and instructional videos. Some are attached to higher-education institutions.
2 STUDIO TYPES
32.1 Relationship diagram for sound recording studio suite
background noise levels. Camera tracking requires a floor laid to very precise tolerances (currently 3 mm in 3 m). The floor is normally heavy duty linoleum sheet laid on an asphalt mastic screed; it requires a specialist floor laying contractor to achieve these fine tolerances. Studio length-to-breadth ratio should be in the region of 1:1.5. The minimum practical floor area for a small commercial TV studio would be 60 m2 with static cameras. TV station studios range between 200 and 400 m2. The studio height is determined by the clear space required below the lighting grid (a function of the longest camera angle). The minimum height for a small studio is 4 m; in the larger studios 11 m to the grid with a clear height above of 2.5 m, making something over 13.5 m overall. In these studios an access gallery is required at grid level approximately 4.5 m above studio floor level. This is normally to avoid obstruction of access doors and observation window. Access to the galleries from studio floor level is mandatory and direct access to lighting grid level is desirable. A cyclorama or backdrop cloth is suspended below lighting grid level. It should be at least 1.25 m away from the walls to allow a walkway around the studio and is on a sliding track with radiused corners to enable it to be stored.
2.01 Sound studios Small sound studios may be used for such purposes as local broadcasting and for recording advertisements and jingles for commercial radio. 32.1 shows the scheme for such a facility. Where larger spaces are required, for example for recording orchestral music, studoios primarily designed for TV might well now be used. The principles behind both sound and TV studios are similar, although sound studios are more likely to have direct vision windows.
2.03 Interview and announcers’ studios These studios range in size from 30 to 60 m2 with a height of 4 to 6 m. Static cameras and a simple form of lighting grid combined with floor lighting stands are used.
2.02 Multi-purpose TV production studios Previously, TV studios differentiated between music and drama. Now, all are multi-purpose largely due to economic pressures. They have accepted acoustically ‘dead’ conditions, reverberation or presence being added electronically. Greater use of zoom lenses in preference to camera tracking means microphones are located further from performers, necessitating low reverberation times and
2.04 Audience participation studios Some productions require audience participation and fixed theatretype seating on terraces is provided. In smaller studios this is demountable, so storage space has to be provided. Audiences place more stringent demands on the planning of a TV complex, as segregated access and emergency escape routes have to be provided (see Chapter 33, Auditoria). 32-1
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Studios for sound and vision
3 PLANNING 3.01 Layout A typical layout for a TV broadcasting studio complex is shown in 32.2. Larger installations will have workshop facilities adjacent to the scene dock and if flats and backdrops are made on-site a paint frame will need to be the full height of the cyclorama curtain. Further details of such facilities will be found in Chapter 33. Equipment areas Ancillary equipment areas will include separate areas for VTR (video tape recording) and telecine (transference of filmed material to video). The machine operator should be able to hear sound track and cues above the noise of other machines in the room which are usually enclosed in open-fronted cubicles with heavily acoustically treated walls. Master control room Adjacent to these equipment areas will be the master control room, which is the last monitoring link in the video and audio chain before transmission. Here programme material, either recorded (VTR and telecine) or live from the studios, will be linked with continuity from the announcer’s studio. Dressing rooms Artists’ facilities adjoining the studio will include dressing rooms with associated wardrobe and laundry, rest and refreshment areas (see Chapter 33).
and striking scenery, and setting up lighting and cameras for productions). These need not be the full studio size as several sets will occupy the studio floor and scenes are rehearsed individually, often in remote assembly halls. Service spaces In addition to the areas detailed in 32.2, space will be required for a sub-station, emergency generator and tape stores. The small commercial and education studios which do not broadcast will have simpler planning arrangements. 3.02 Control suites TV control rooms do not now overlook the studio they monitor for the following reasons: cyclorama track and studio scenery are likely to interfere • The with the producer’s view; production decisions are made off monitor screens.
chroma of glass in the observation windows must be • The adjusted to confirm colours reproduced by TV monitors. This
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is done using an applied tinted finish which requires frequent replacement. Windowless production suites do not need to be elevated, hence production staff have direct access to the studio floor. A typical control suite layout of this type is shown in 32.3.
Rehearsal spaces Separate rehearsal spaces are required as there is considerable pressure on studio floor time (much of which is used in setting
32.3 Layout of a production control suite with no direct visual access to studio
Minimum clear height in the control room, including a false ceiling for services, is 4 m. Separate control areas for production, lighting, and sound are required with 25 dB insulation between each and visual contact via observation windows. A viewing area for visitors separate from that for production staff is desirable. The disadvantages of such a layout is that the producer has no direct visual contact with the floor manager or performers.
4 SERVICES
32.2 TV studio complex; block planning diagram
4.01 Lighting Television studio lighting is highly specialised. The large production studio will have a remotely operated lighting grid, whereas the small studio will have a simple pre-set system.
Studios for sound and vision
Lamp support systems There are three basic types of lamp support systems: most elaborate is a grid of ‘railway’ tracks covering the • The whole studio. On these tracks run carriers which have a tele-
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scopic arm holding the lamp. The arm is motor driven (either electrically or hydraulically) and lowers the lamp to studio floor level for setting and adjustment. Each lamp can be separately panned, tilted and dimmed remotely. An additional overhead rail at the perimeter of the grid will carry carts on to which the ‘monopole telescopes’ and lamps can be run off the grid to a lamp store. Where several studios exist this rail will interconnect them all via a central lamp store. The latest grids are equipped with an electronic memory to enable a whole production of lighting settings to be stored. A simpler form has lighting bars which can be raised or lowered electrically or manually fixed direct to the studio. The bars take several forms from the ‘lazy scissors’ principle to a simple bar on cables and pulleys. The third and simplest type is a fixed barrel grid. As in the second type no space is required above this grid for access as lamps are clamped direct to the bars and set from studio floor level.
Lighting to equipment and control areas needs to be carefully studied to avoid reflections and provide correct levels for viewing. Special fittings are often required. 4.02 Air conditioning Air conditioning presents the designer with a number of unique problems: the large volume, the high heat loads generated by lamps, low background noise levels and the need to provide comfortable conditions in parts of the studio obscured in all but one plane by scenery. Low air speeds have to be used to achieve the noise levels. The most successful system has been the ‘dump’ system where cooled air is fed from a large plenum chamber above grid level and returns via natural convection of heat from the lamps to a similar exhaust plenum at an even higher level. Plant rooms, unless remote from the studios, require structural isolation to prevent vibration transmission (see para 5.03); adequate space must be allowed for attenuation. Mechanical engineers are familiar with duct-borne noise problems, but do not normally investigate noise break-in through duct walls or the architectural acoustic problems. The architect should make certain that this forms part of the specialist consultant’s brief. 4.03 Technical wiring Extensive provision has to be made for power, audio and video wiring connecting the studio to control suites and equipment areas. Camera cables are approximately 50 mm in diameter and have a minimum bending radius of 0.5 m. Power wiring, which may include low-voltage power, has to be run in separate trunking from audio wiring to avoid interference. Trunking is often concealed within the acoustic finishes and all perforations of the studio enclosure have to be sealed airtight to avoid sound transmission.
5.02 Airborne sound insulation For every location a full one-third octave band, site noise level survey must be carried out to determine the design of the enclosing structures. Additionally, all internal transmission loss defined by frequency should be established and can be extended to provide the mechanical engineer with the requirements for in-duct crosstalk attenuation. For this it will be necessary to establish the maximum permissible noise levels from all sources in each room.
5.03 Vibration isolation The noise and vibration levels of all mechanical plant should be studied and the architect must identify who should be responsible for defining maximum permissible levels and designing to achieve them. Structure-borne sound transmission, particularly on the upper levels of framed buildings, may necessitate the ‘floating’ of plant rooms and noise-protected areas. This involves isolating the walls, floor and roof from the surrounding structure. The walls are built off a secondary floor bearing on steel spring or rubber carpet mountings designed to a maximum natural frequency not exceeding 7 to 10 Hz. Footfall impact noise often requires floors to be carpeted with heavy underfelt or in extreme cases, the floating of studios.
5.04 Reverberation time 32.4 relates reverberation time to volume for television studios. Calculation will indicate the amount and type of absorption required. Details of a typical wide band modular absorber are shown in 32.5. Approximately 200 mm should be added to the clear studio height and to each wall thickness to accommodate the acoustic treatment. Sound control rooms need to be similarly treated, with the other production control rooms and technical areas made as dead as possible.
5.05 Background noise levels Maximum permissible background noise levels are shown in 32.6. These should be related to the external ambient levels and to noise from air-conditioning plant. In certain situations where plant rooms are adjacent to noise-sensitive areas, maximum permissible noise levels at intake and extract louvres should be specified to limit this noise breaking back in through the external skin, particularly at windows.
5.06 Special details Acoustic doors and sound lock Typical details for an acoustic door and an observation window are shown in 32.7 and 32.8. All noise-sensitive areas should be approached via a sound lock lobby consisting of acoustic doors, with either end of the lobby treated to be acoustically dead. The mean sound transmission loss of each door is 33 dB and sealing is affected by means of magnetic seals.
4.04 Other services Large production studios will require compressed air, gas, water (including drainage) and a smoke-detection system, in addition to electrical services.
5 ACOUSTICS 5.01 Identify standards The standards to be achieved should be identified by the specialist consultant and agreed with the client at the outset. The two main sources are the BBC and the ISO (International Standards Organisation).
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32.4 Reverberation times for TV studio
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Studios for sound and vision
32.5 Modular sound absorbing unit 32.7 Acoustic door construction
32.6 Background noise levels
32.8 Observation window
Studios for sound and vision
Scenery doors The transfer of scenery into the studio requires an opening in the region of 5 m high by 5 m wide with a sound reduction index between 50–60 dB. This door will almost certainly be of steel construction. Hinged doors have been used but the forces required to ensure that the edge seals close airtight produce operational difficulties. A ‘lift and slide’ door is more satisfactory. An electric or hydraulic drive opens and closes the door while radius arms lower it inwards and downward to compress the edge seals all round. This type of door does not require an upstanding threshold as does the hinged door, and this is a considerable operational advantage.
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6 STATUTORY REQUIREMENTS Careful examination should be given at the planning stage to means of escape and fire resistance. Statutory requirements vary considerably in all parts of the world, but the most stringent are those operated in the UK where Class O flame spread may be required for all finishes and up to a four-hour fire separation for the studio walls. This necessitates double steel roller shutters on all perforations through walls. Smoke vents are sometimes required and these must be designed to match the sound insulation of the roof.