Two masses separated by a low frequency response isolator create the environment for noise and impact reduction many times greater than a single mass of equal weight. The isolator seeks to emulate the stiffness properties of the air, but as this space increases the frequency of the isolator governs the frequency of the floor system. If noise reduction is the primary goal then enveloping walls usually rest on the isolated floor. Ceilings with their own isolators cap the construction. If the frequency range is above 20 hz, neoprene is generally the best choice. If vibration or impact reduction is required, springs supporting the isolated floor by itself will normally suffice. The professional acoustician is the best person to make these evaluations. Thirty years ago several manufacturers working with Riverbank Acoustical Laboratories tested an isolated room under ideal conditions. Much of what was learned for attenuating high frequency noise (above 20 hz) had long been practiced by Aircoustics.
MOST IMPORTANTLY, ONCE THE ABOVE CRITERIA IS ESTABLISHED, IT IS THE ISOLATOR'S NATURAL FREQUENCY WITH DYNAMIC STIFFNESS RESPONSE AND ITS CONTINUING LONGEVITY THAT WILL EFFECT THE STC & IIC (IMPACT INSULATION CLASS) OF A PROTECTED SPACE!
Natural Frequency establishes the response from one slab to the other. For the control of high frequency noise, 10 hz is the established criteria including dynamic stiffness procedures are critical as is ongoing verification of quality control. Long test histories have shown that 2" of air space should not be diminished.
The ANFF neoprene floor isolators all perform below 8.5 hz. Compounding is to AASHO specifications and molding occurs in the United Arab Emirates under the supervision of the Aircoustics quality control.
FLOATING FLOOR DESIGN
The floating floor shall consist of a 4"(100mm) thick concrete slab isolated from and supported 2 2" (62mm) above the waterproofed structural slab by resilient neoprene isolators covered by3/4" (18mm) plywood panels that form the pouring surface.
The floating floor slab shall be isolated from adjoining walls and curbs by means of perimeter isolation board.
Any floor drains, piping, conduit and duct penetrations must not short circuit the isolation system.
Any equipment within these rooms shall be mounted on housekeeping pads or directly on the floating floor as shown on the drawings.
In seismic zones the floating floor shall be restrained horizontally by curbs or walls designed to withstand the horizontal seismic forces. Solid bridge bearing neoprene pads shall be interspersed between perimeter isolator fiberglass to withstand the seismic forces with a maximum deflection of 0.2"(5mm).
B. Performance Requirements
The floating floor system shall have a minimum rating of STC-79 and INR+17 as verified by an independent laboratory in prior tests.
C. Floor System Construction Procedure
The setting of all isolation materials shall be performed by or under the supervision of the isolation manufacturer.
Set and waterproof any drains and lower pipe seals in keeping with waterproofing specifications.
Cement perimeter isolation board around all walls, columns, curbs, etc. 3a. In seismic zones intersperse the perimeter isolation board with bridge bearing quality neoprene pads the thickness of the isolation board.
Place individual neoprene isolators on the sub-floor at a maximum spacing of 24"(600mm) in strict accordance with the approved drawings prepared by the isolation manufacturer. Additional reinforcement must be detailed on isolation manufacture=s drawings when required.If sound barrier isolation walls are used, add the following: Perimeter isolators shall be selected to support the wall weight in addition to the perimeter of the floating floor.
In seismic zones provide anchorage for the double acting resilient vertical snubbers to the structural slab. Snubber anchor bolts must be in close proximity to the mechanical snubbers restraining any high center of gravity equipment to withstand the overturning moments generated by the machinery snubbers and prevent failure of the floating floor.
Cover isolators with 3/4"(18mm) AC plywood. Isolators shall be located under joints and joints staggered. Connect plywood at abutting edges and corners with 16 gauge steel junction plates.
Cover the plywood with 6 mill (0.15mm) plastic sheeting and carry it up the walls past the perimeter isolation.
Place seismic snubber housings on the anchor bolts that protrude from the structural floor and through the plywood.
Place reinforcing as shown on the drawings and pour floor monolithically.
After the concrete has hardened, caulk all perimeter isolation board. If sound barrier walls are used, add the following: Construct block walls on the floating floor being careful that mortar does not drop behind the walls. Place 2"(50mm) fiberglass bats against the structural wall as a precaution. Provide sway braces and isolated angle iron wall braces at the top of the walls. Caulk angle iron braces.
In seismic zones adjust the double acting snubbers after machinery is in place to provide a maximum up and down clearance of 0.125"(3mm).
Detailed product drawings and load and deflection curves of all isolators.
A drawing or drawings showing:
Dead, live and concentrated loads.
Isolators sizes, deflections, frequencies and locations.
Any drain and penetration locations.
Size type elevation and spacing of concrete reinforcement.