| In a this test, a smaller
assembly was constructed with wood studs, resilient channels,
and gypsum wallboard. Penetrations were made for a single
and back-to-back metal electrical boxes, as shown in the graphs
to the right. The assembly was tested with:
- No Insulation
- Fiber glass batt insulations
- BIBS Insulation system
In order to simulate a field installation, instead
of laboratory conditions, R-11 kraft-faced insulation was cut
with up to a 1/8" gap around all three metal electrical boxes.
No insulation was installed between the back-to-back electrical
boxes.
High sound levels were generated on one side of the assembly,
and sound energy was transmitted through the panel. On the quiet
side of the assembly, a sound intensity probe was used to scan
the surface, measuring regions of locally high and low sound
intensity levels.
Sound intensity contour maps were generated from the experiment
to graphically display the sound energy transmitted through
the wall. The colors indicate local regions of local regions
of high and low sound transmission.
The contour maps clearly show the leakage through the back-to-back
electrical box penetrations, and slight leakage from the single
metal electrical box penetration.
The three tested assemblies show great contrast in their overall
levels, and demonstrate the importance of quality installation
in sound-rated insulated assemblies. The small gaps in the R-11
batt insulated assembly can clearly reduce the effectiveness
of the sound control of the wall in the 500 to 2000 Hz frequency
range. With the Blow-In-Blanket System and professionally-trained
BIBS installers, the gaps, are virtually eliminated and superior
sound control is achieved. |
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