A gypsum board partition is tested as Selection
would increase the TL (over a single wall of compa-
in item 10. The TL for this "Type 1" partition is ob-
rable weight) by about 10 to 15 dB in the low-
frequency region and 30 dB or more in the high-
tained from table 512 of the N&V manual. The TL
frequency region-- if there were no rigid structural
of a 2-in. -thick solid wood door (9% of wall area) is
combined with the TL of the gypsum board (using
ties joining the two walls of the double wall. The
para 54e and fig. 53 of the N&V manual), and the
floor, ceiling, columns, etc. serve as structural con-
resulting TL is inserted as Selection B of item 10.
nections, so these full amounts of TL improvement
This wall combination fails to meet the require-
will not be reached. Even so, a rough estimate of
ment by 1 dB in the 125-Hz band. However, this is
the TL of this double wall structure can be made.
considered an acceptable selection, because low-
First, the total surface weight of both walls is esti-
2
mated to be about 64 lb/ft. (52 for the 10-in.
frequency structureborne and earthborne vibration
hollow-core concrete block and 12 for gypsum
may limit the low-frequency sound levels that can
board partition). The TL of a single wall of this to-
be achieved anyway. Also, the vary narrow (4-ft.
tal weight is approximately that of a 12-in .-thick
wide) corridor leads to an inaccurate SPL estimate
hollow-core concrete block wall (from N&V table
in the low-frequency region (where the corridor
59). It can be assumed that the TL improvement
width is much smaller than the wavelength of
sound). If lower SPLs in the office are necessary,
attributable to the 48-in. corridor width will be
the "Type 2" stud partition of the N&V table 512
about 50 percent of the amount shown in the N&V
would provide 6 to 8 dB lower levels via airborne
table 5-5 (extrapolated to a 48-in. air space) at low
frequency, rising to about 90 percent of the amount
paths in the low-frequency region.
shown in that table at high frequency. However,
because of high-frequency sound leakage and
(c) The second possible approach to ob-
flanking paths, it is doubtful that actual TL values
taining the office SPLs treats the corridor simply
would go much above about 70 dB for this particu-
as a double wall. The TL is not precisely known,
lar structure. The resulting TL estimate is shown
but can be roughly estimated with the use of figure
in item 6 of figure 422.
55 of the N&V manual. A 48-in. -wide corridor
4-31
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