320
Ceilings: Acoustics
325
325.1
COMBINED FLOOR AND CEILING
The combined floor and ceiling construction should provide ratings of STC
50 and INR +5 between floors. The higher ratings of STC 55 and INR 10
which are required between service areas and patient rooms (Hill-Burton
standards) are not applicable to the floor/ceiling construction, since the
planning rules of the Prototype Design always separate the service bay
from the rest of the service module by means of a two-hour wall, and the
ceiling over the functional space is interrupted at this wall. The planning
rules also preclude the placement of a service bay over functional space
on the floor below.
Since there is no acoustic data currently available for assemblies of a type
similar to the Prototype Design, the acoustic performance of the combined
floor and ceiling can only be estimated. It is expected that both the impact
isolation and the airborne sound isolation from floor to floor will be
satisfactory, assuming a fairly dense structure for the platform.
325.2
COMBINED PARTITIONS AND CEILING
The ceiling construction must not reduce the sound isolation provided by
the partitions. The combined partition and ceiling construction must
provide STC ratings as high as 50. In order to achieve this high level of
performance in the field, the joint between the partitions and the ceiling
must be carefully detailed, installed, and supervised. The degree of
supervision during construction can seriously affect the acoustic
performance of the system. The joint should be detailed so that acoustic
seals are relatively accessible for inspection and repair.
325.3
PLATFORM
Materials must be selected in reference to the maximum noise level to be
allowed in patient bedrooms and other critical areas. The platform should
provide a minimum of STC 40 to protect habitable spaces from noise
generated by activity or equipment in the service zone. It is not expected
that the platform alone will provide good impact isolation from the floor
below, but since the service zone will be infrequently occupied, this is not
expected to present any serious problems. Vibration and noise producing
items in the service zone should be isolated from direct contact with the
ceiling by resilient mounts.
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