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The interior gi slab to close > end to the PIot

Figure 16.26 Flanking around Slabs at Curtain Walls

Section Drawing

The interior gi slab to close > end to the PIot

Flanking paths sometimes occur at column penetrations of slabs, particularly where the lower floor space has an open ceiling. In each of these conditions the openings around the column must be closed off with a material that has a sound transmission loss equivalent to the floor system.

Divisible Rooms

Moveable walls, used as dividers between meeting rooms, are commercially available with STC ratings as high as 50 or more. To achieve these ratings the panels weigh as much as 10 lbs/sq ft (49 kg/sq m). They are supported from a structural framework above that must be sized to carry the load without undue deflection. Unless this is taken into consideration the moveable walls can drag on the floor when they are moved into place. Some deflection is inevitable, and the panels are positioned and jacked up so that they support their own weight from the floor below. Moveable walls are the same as permanent walls in that the plenum flanking path must be blocked off. Figure 16.27 shows a design. Any stem wall must also accommodate structural deflection due to the weight of the panel.

Masking in Closed Offices

Where walls do not extend to the structural deck above the T-bar ceiling, it is not possible to achieve Confidential Privacy without the addition of masking sound. An office separation might consist of a single metal-stud wall with single layers of 1/2" gypsum board extending up to or slightly above the T-bar and a mineral-tile ceiling. Return-air grilles should be baffled with a lined sheet-metal enclosure illustrated in Fig. 16.28, with the open sides facing away from the receiver room. Table 16.10 shows the resulting degrees of privacy with this configuration for several levels of masking sound.

Figure 16.27 Installation of Moveable Wall Partitions

A wall of equivalent transmission loss should be built above the moveable wail. Studs and batt not shown for clarity.

Figure 16.27 Installation of Moveable Wall Partitions

A wall of equivalent transmission loss should be built above the moveable wail. Studs and batt not shown for clarity.

Figure 16.28 Return Air Boots

A sheet metal return air boot built over the return air grille. Orient the opening away from the receiver. Nominal dimensions 24" x 24" x &" high.

A sheet metal return air boot built over the return air grille. Orient the opening away from the receiver. Nominal dimensions 24" x 24" x &" high.

Table 16.10 Closed Office Speech Privacy for Mineral Tile Ceilings Normal Voice Levels (Chanaud, 1983)

No Masking Masking

Attenuation (NIC) 33 33

Masking Level (dBA) 35 39

Privacy Index 89 95

Degree of Privacy Normal Confidential

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