(NC/RC 35 or lower), the maximum intrusion level of
In such locations, an acoustical report shall be submitted
elevator noise shall be limited to 5 dB below the
showing that the building's acoustical design mitigates
maximum NC/RC for the space in all octave bands.
the intrusion of exterior noise to no more than 5 dBA
over the maximum mechanical noise levels (Table 3-5,
All hot-water heating, supply, waste, and drain piping
Column 1).
shall be vibration isolated from the structure, as well as
from other piping, ductwork, gypsum board, etc. in the
For locations where a railroad runs beneath or abuts the
walls, ceilings and floors enclosing noise sensitive spaces
site, a newly constructed building shall contain provisions
(Table 3-5, Column 2, NC/RC 35 or less). All stud and
that minimize vibration transmitted to office spaces
joist spaces where such piping is located shall have R-11
within the building, including feelable vibrations and
(3-1/2-inch thick) batt insulation installed, and piping
vibrations in the form of audible noise.
shall not be closer than one-inch to gypsum board.
Mechanical and Plumbing Noise. All mechanical
Noise isolation, room acoustics and speech privacy.
equipment shall be vibration isolated per ASHRAE
Absorptive materials are required in speech sensitive
standards and guidelines, including spring isolators,
spaces to control reverberation and echoes. Table 3-5,
inertia bases as well as ancillary items such as flexible
Columns 2 and 3 lists spaces that require absorptive
piping and electrical connections. In seismic areas,
finishes. The first number in each column refers to the
acoustical vibration isolation must not compromise
minimum level of the material's performance; the second
seismic code requirements and vice-versa. As such,
refers to the minimum percentage of the ceiling or wall
housed springs should be avoided; instead, un-housed
that must have finishes achieving this performance.
springs with separate seismic snubbers should be used.
Floor/Ceiling assemblies separating office spaces shall
Ambient noise from mechanical equipment shall not
achieve an NIC of not less than 50 (when furnished) and
exceed noise criteria (NC) values shown in Table 3-5,
Field Impact Isolation Class (FIIC) of not less than 50.
Column 1, "Mechanical Noise". Diffusers with an NC
Table 3-5, Column 4 lists the minimum noise isolation
rating 5 points less than the noise criterion for the space
(NIC) for spaces requiring acoustically rated walls.
being served are required.
For constructions on suitable slab floors, when properly
Where occupied space occurs adjacent to, above or below
detailed and constructed, and with all connections
mechanical, electrical equipment, or machine rooms, or
caulked airtight with acoustical sealant, the following wall
adjacent to HVAC or elevator shafts, the intervening
assemblies will satisfy the minimum specified NIC
structure (partitions, shaft walls, doors, floor and ceiling
requirements, with the offices furnished typically. Doors
assemblies, etc.) shall be sufficient to control noise
and other holes in the walls will degrade the overall
intrusion to no greater than the maximum noise criteria
performance. These wall examples are not the only
(NC) or room criteria (RC) values shown in Table 3-5,
constructions that will satisfy the performance criteria,
Column 1, "Mechanical Noise". Where an elevator shaft or
but are intended solely to provide guidance on projects
equipment room occurs adjacent to noise sensitive spaces
that do not require a qualified acoustical consultant
during the design phase.
79
ARCHITECTURAL
AND
INTERIOR
DESIGN
3.4
Special Design Considerations
Revised March 2005 PBS-P100
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