Speech Privacy In Closed Offices

Private Offices

In a closed office the assessment of privacy is expressed in terms of STC values between adjoining spaces. Closed offices have the advantage of providing privacy throughout the enclosed space for a standing or seated occupant. The disadvantage is that the normal background level is lower, even when masking is included, and conversations may take place at raised voice levels even when confidential matters are being discussed. Specialized areas such as psychologists' offices, spaces used for conflict resolution, rooms with audio visual systems, lecture rooms, and classrooms, are all likely to have a need for extra isolation and should be identified as part of the initial planning process.

The analysis of sound transmission for private offices is similar to that for open offices. In critical locations detailed calculations using voice spectra, transmission loss, and background noise levels should be done. Figure 16.20 shows the calculated Articulation Index for various FSTC values at three voice levels, and Table 16.9 includes the corresponding sound attenuation requirements for various degrees of privacy. Chanaud (1983) recommends that the FSTC of a given structural component be 6 dB greater than the desired composite FSTC.

Full-Height Walls

The traditional approach to closed-office privacy is to use full-height walls and weather-stripped solid core doors. When the walls are full height, the total FSTC value is obtained. Sketches of several wall configurations are given in Fig. 16.21, along with estimates of their composite FSTC values. When the wall does not extend full height on both sides various plenum barrier materials can be used to make up the difference.

For Confidential Privacy with a normal voice talker, a good separation wall between rooms is a single 3 5/8" (90 mm) metal stud with 5/8" (16 mm) drywall each side and R-11 batt in the airspace. This wall rates an STC 44 (FSTC 39), and for voice provides a calculated noise reduction of approximately 42 dB. In terms of a rough calculation, a 60 dBA

Figure 16.20 Required FSTC for Speech Privacy for Various Voice Levels (Chanaud, 1983)

Background level = 44 dBA (Room 2)

Figure 16.20 Required FSTC for Speech Privacy for Various Voice Levels (Chanaud, 1983)

Background level = 44 dBA (Room 2)

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