Structural Floor Panels Design Guide - Hebel Supercrete AAC ...

1.3.3 Impact Noise
Some of the most difficult sound sources to block with
a floor are those caused by direct impact, or vibration of
the floor/ceiling structure. Heavy foot falls, the rumble of
wheeled trolleys, luggage etc being dragged and a seemingly
endless variety of thumps, bumps and scraping sounds add
to the airborne noise previously outlined.
Structural supports in many floor systems, such as timber
joists or bolted steel members can all creak and groan and
emit squeaks, especially if timber has dried and shrunk over
time, allowing small movements against one another, or
where nails and screws become loose due to this drying
shrinkage.
No floor system that has a continuous, direct physical
connection between floor structure and the ceiling
structure below, will ever effectively isolate impact noise.
When people walk over the floor, tiny movements and
vibrations in the floor element are transferred through
the directly fixed ceiling battens or supports and into the
sheeting material of the ceiling. The vibrations in the ceiling
sheet oscillate the air in the room below the noise source,
and this moving air transfers the noise to the listener below.
We have all been in downstairs rooms and heard the noise
of people or objects moving in rooms above. This is impact
noise.
Table 2. No Floor Covering
Floor
Thickness
1.3.4 Impact Insulation
To effectively block impact noise, the first and most effective
principle is to isolate the ceiling, to prevent it vibrating like
the skin of a drum, every time the floor above receives an
impact. This can be done in a variety of ways, but the most
common is to suspend the ceiling on wires or threaded
rods, fitted with clips to support the steel ceiling battens,
or mounting grid. By hanging the ceiling, rather than
direct fixing it to the underside of the floor, much of the
vibration can be dissipated. The resulting ceiling cavity is a
useful space for services such as lighting, plumbing and air
conditioning, but care must be taken to ensure that these
items are also properly mounted and insulated to prevent
noise transfer. Supplemental insulation batting is usually
fitted into the ceiling cavity to assist in isolating and baffling
both airborne and impact noise. Alternatively, if space is at
a premium, specialist acoustically resilient clips are available
for direct fixing to the panel underside.
To test the effectiveness of the impact noise insulation
within a floor assembly, a test is performed with a tapping
machine which emits vibration by direct impact on one side,
and the transferred sound is measured on the other. This
establishes the Impact Insulation Class or IIC.
As with STC, the IIC rating required by the New Zealand
Building Code for inter-tenancy floors is IIC 55, or
approximately 55 decibels of sound reduction.
Supercrete Structural Floors are not only ideal for
blocking airborne noise, but when fitted with a suspended
ceiling below and an insulated ceiling cavity, achieve intertenancy
quality impact insulation class.
Ceiling Cavity Resilient Insulation Batt Plasterboard Number of Airborne Noise Impact Noise
Space (mm) Hangers thickness ceiling lining lining sheets STC or Rw Rw+CtrRw Ctr Floor IIC Lnw+C1
150 0 No Nil None 0 43 39 -4 30 79 1.27
150 0 No Nil 13mm 1 44 40 -4 30 79 1.32
150 28 No 25mm 13mm 1 53 45 -7 31 78 3.27
150 28 No 25mm 13mm 2 55 48 -7 32 77 3.32
150 50 Yes 50mm 13mm 1 56 47 -8 40 69 3.27
150 50 Yes 50mm 13mm 2 60 50 -10 43 66 3.32
150 80 Yes 50mm 13mm 1 60 50 -10 48 62 3.27
150 80 Yes 50mm 13mm 2 64 56 -8 52 57 3.32
150 80 No 50mm 13mm 2 57 54 -4 37 72 3.32
Thermal Insulation
R-value (m.2K/W)
200 0 No Nil None 0 45 40 -4 32 76 1.52
200 0 No Nil 13mm 1 45 41 -5 32 76 1.61
200 28 No 50mm 13mm 1 54 46 -8 33 75 3.56
200 28 No 50mm 13mm 2 56 49 -7 34 74 3.61
200 50 Yes 50mm 13mm 1 57 48 -9 42 66 3.56
200 50 Yes 50mm 13mm 2 61 51 -10 45 63 3.61
200 80 Yes 50mm 13mm 1 61 51 -10 50 59 3.56
200 80 Yes 50mm 13mm 2 66 57 -9 54 54 3.61
200 80 No 50mm 13mm 2 60 55 -4 39 69 3.61
250 0 No Nil None 0 47 42 -5 34 75 1.81
250 0 No Nil 13mm 1 47 42 -5 34 75 1.90
250 28 No 25mm 13mm 1 56 47 -9 35 74 3.85
250 28 No 25mm 13mm 2 58 50 -8 36 73 3.90
250 50 Yes 50mm 13mm 1 59 50 -10 44 65 3.85
250 50 Yes 50mm 13mm 2 62 51 -11 47 62 3.90
250 80 Yes 50mm 13mm 1 62 51 -11 52 58 3.85
250 80 Yes 50mm 13mm 2 67 57 -10 56 53 3.90
250 80 No 50mm 13mm 2 61 56 -5 41 68 3.90
Floor/ceiling assemblies shown shaded meet NZBC intertenancy requirement for STC55 and IIC55
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