Sound Stages

Sound stages are large open rooms used for indoor movie production. Acoustically they are designed to be dead with all surfaces except the floors covered with 4 to 6 inch (100 to 150 mm) deep blankets of absorptive material. The floors are smooth and flat so that cameras can be dollied. The exposed wall surfaces can be faced with commercial quilted blankets covered with hardware cloth below an elevation of 10 ft (3 m). The best rooms are built with isolated construction, floated floors, double-studded walls, and separately suspended gypboard ceilings. Access is provided via sound rated doors, which can be quite large. Some facilities have control rooms adjacent to the stage for mixing and recording.

The most difficult aspect of sound stage design is noise control. Isolation from exterior noise is a challenge because many stages are built in converted warehouses with lightweight roofs and little thought to the isolation of traffic and aircraft noise. Large air conditioning

Figure 21.24 Abbey Road Studio One, London, England (Abbey Road Studios, 2001)

units are required to cool the stage lighting fixtures and this equipment is often located on the roof, where it is difficult to control. It is much preferable to separately support air handlers on grade or on an elevated steel platform dedicated to that purpose. Ductwork should be isolated from the structural framework either by resilient suspension or by a separate support system. Silencers located at a roof or wall penetration provide exterior as well as equipment noise control.

Scoring Stages

Scoring stages are rooms in which the music for a film is recorded. The orchestra conductor, who is the composer, faces both the musicians and a large screen on which the film is projected. As he conducts, he may listen through a single headphone to a click track, which aids in synchronization of the film and the score. Visual cues are also projected onto the screen in the form of streamers that progress from left to right across the screen to mark the beginning of a transition or effect when they reach the right-hand side.

A scoring stage is large, almost the size of a concert hall. Like concert halls, the best ones are shoebox-shaped with high ceilings and irregularly shaped diffusers on the walls and ceiling. A very good one, Studio 1 at Abbey Road Studios in London, is shown in Fig 21.24. Its dimensions are 92.6 ft x 59.7 ft x 39.4 ft high (28.2 m x 16.1 m x 12.2 m) and its total volume of 218,000 cu ft (6172 cu m) is about one-third that of Boston Symphony Hall. On one end there is a large (44 ft or 13.4 m wide) projection screen with the control room in an opposite corner.

Scoring stages are designed much like concert halls but without the requirements for an audience. The floors are flat and the walls and ceiling surfaces feature irregular shapes for diffusion. Reverberation times can be changed using moveable curtains or panels. For film, from 5 to 8 mics are used for the right-center-left and surround signals, and another 30 to 35 mics for individual instrument groups. The high ceilings sometimes make it difficult for the musicians to hear each other so 12 to 18 foldback channels are provided from the mix board to individual players through headphones. The orchestra can be seated on risers for visual cohesion and arranged to achieve a balanced sound.

Figure 21.24 Abbey Road Studio One, London, England (Abbey Road Studios, 2001)

Control Room

Machine Room

Control Room

Machine Room

Since sound stages are smaller than concert halls the orchestra cannot play quite as loudly as they would under performance conditions. When they do, the reverberation in the room, particularly the bass, can overwhelm the direct sound and yield a muddy recording. If the balance is correct and the control room is set up properly, the recording engineer can do a live mix including surrounds if necessary, however, the recorded tracks can be remixed at a later time.

The reverberation characteristics of a scoring stage are much the same as a concert hall. Abbey Road has a mid frequency reverberation time of about 2.2 seconds, rising slightly at lower frequencies and remaining fairly constant at high frequencies. The lack of audience and seat absorption limits the falloff of the high frequencies to that due to curtains, musicians, and air absorption so these rooms can be somewhat brighter than a performance hall.

The recording of symphonic music can also be done in an empty concert hall. In these cases the room is often extensively modified to accommodate this use. For example, when Royce Hall at UCLA is used for recording, a wooden platform for the musicians is constructed over a portion of the seating area and the opera chairs in the orchestra section are covered with 3/4" (19 mm) plywood over visqueen sheets to decrease high-frequency absorption (Murphy, 2001).

Recording Studios

Recording studios consist of one or more rooms where music is played and recorded. The musicians may all be present at the same time or they may never see one another. With the ability to move recorded music from place to place electronically, musicians may perform in rooms a continent away and days or weeks apart. When musicians are playing simultaneously, separate rooms are desirable to isolate the instruments so that they do not bleed into other microphones. These isolation booths also can be helpful in generating different acoustic environments.

A good studio must incorporate several acoustical factors:

2. Noise isolation from other areas (including footfall)

3. Freedom from acoustical defects such as flutter

4. Adequate absorption (often variable)

5. Reasonable diffusion

6. Isolated areas for recording individual instruments

7. Visual communication between the control room and the studios

8. Control of bass reverberation and modal buildup

Studios can be generic or highly personal, based on the working preferences of an individual user. A good example of the latter is Hum Studio in Santa Monica, CA, designed for Jeff Koz, a well-known composer. Figure 21.25 shows the floor plan for the main studio and control booth. Since most of the composition work is done at a keyboard with small digital mix boards, the traditional control room layout was not used. Instead, three work stations, each with a mix board, were arrayed along the front and side walls. Each could be used simultaneously during recording and mixing sessions. The main composing station was designed around the users' equipment. Since listening is done via small near-field loudspeakers, there was no need for large stereo monitors and no need for a large loudspeaker

Figure 21.25 Hum Studio A, Santa Monica, CA, USA (Acoustician: Marshall Long Acoustics) (Architect: Walter Meyer Associates)

Figure 21.25 Hum Studio A, Santa Monica, CA, USA (Acoustician: Marshall Long Acoustics) (Architect: Walter Meyer Associates)

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