MIL-HDBK-1191
a.
Area of Partition:
12.5 feet x 8 feet = 100 square feet
Area of Door:
3 feet x 7 feet = 21 square feet
Therefore, the door is 21% of the total wall area
b.
If the STC of the partition is 38 dB, and the STC of the door is
30 dB, the difference between the two STC values is 8 dB.
c,
From Figure 23.4, the reduction of the NR of the partition is 5
dB.
d.
Therefore the total STC of the composite construction is 38 5 =
STC 33.
23.2.4
Proposed Ratings and Criteria.
23.2.4.1
Accepted Standards for STC ratings. Constructions should be
selected to meet the STC ratings listed in Appendix "A". STC values should be
determined for composite constructions. See Section 23.2.3 above. Where
partitions do not extend to the structure above, sound transmission through
ceilings must be considered in the determination of the composite STC
performance. See Section 23.2.2.2 above.
23.2.4.2
Other Design Considerations. Following are pertinent detail
issues to address in the design. Detailed discussion of all these items is
covered in other parts of this section.
a.
Ceilings: Sound transmission through the ceiling plenum by way of
the suspended ceiling systems must be addressed through upgrading
the ceiling path or with a plenum barrier. See Section 23.2.2
above.
b.
Partitions: Include acoustical caulking at the tops and bottoms
of partitions. See Section 23.2.2.1.b above.
c.
Doors: Interconnecting doors between sensitive spaces should have
perimeter gaskets in order to create an air-tight seal. Avoid
undercutting or door louvers at these door locations. Sensitive
spaces are rooms that require a high degree of privacy, such as
interconnecting exam or treatment rooms, or provider offices. See
Section 23.2.2.4 above.
d.
Equipment noise: Watch for sounds produced by noisy items of
equipment in special purpose rooms, where the noise is transmitted
through walls and ceilings into adjoining spaces. A notable
example is a toilet room with wall-hung fixtures adjacent to a
conference room. See Section 23.2.2.1.d above.
e.
Cross-talk: Sound can be transmitted through short ventilation
ducts with registers in different rooms. See figure 23.7 for
suggested duct layout to avoid this problem and as discussed later
in this section.
f.
Flanking: Sound transfer can easily occur through poorly designed
or installed recessed light fixtures in the ceiling, through
electrical outlet boxes, or other penetrations located opposite
each other on a party wall. See Section 23.2.2.1.b and c, and
23.2.2.2.e.
23.2.5
Structure-borne sound isolation. Structure-borne sound refers to
sound whose energy is transmitted directly into and through the structure of a
building. The most common single-number rating system to evaluate and compare
isolation of impact sound of a floor/ceiling system is the Impact Insulation
23-5
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