AI Cat 2009 13/3/09 16:05 Page 18
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Quiet please
D Sujan, Sr. Materials Development Engineer and Mike Brock, Sr. Market
Development Specialist, Rogers Corporation, discuss how engineered silicone
polymers help reduce noise in VIP aircraft interiors
For most of us who fly on the typical commercial acoustic design mitigates both noise modes by (FAR25.856). The composite structure often
jet the noise level inside the cabin is often an using various design techniques that often includes both a noise barrier and an absorbing
afterthought. The noise is recognisable, but require targeted materials. In addition to material (fibreglass batting or foam).
often not important enough to think twice about. reducing noise, the materials must meet strict Silicone materials and composites are often an
But for private aircraft, it is often a design flammability, smoke, toxicity, weight and durability excellent choice for aircraft applications due to
requirement to have an especially quiet cabin. requirements demanded by the aircraft industry. their excellent flame, smoke and toxicity
Acoustic requirements within the “VIP” cabin are Due to an aircraft’s enclosed environment, performance. Also, silicone based polymers
typically more demanding, requiring a custom the material’s ability to not propagate fire is maintain physical properties over a wide
design approach. truly a critical property. Materials used to temperature range (temperature stability) along
There are two modes of noise typically found isolate vibration of interior components or with great environmental resistance, specifically
on aircraft: structure-borne and airborne noise. block outside noise must meet the strict very low water absorption. Silicone properties
Structure-borne noise is generated by the flammability requirements of the aviation have been known to show very little ageing
vibration of interior components, while airborne industry. While many materials meet the effect, making them a reliable choice for
noise is from the sound of the engines or 12-second and 60-second vertical burn installations that need to be in place over an
aerodynamic flow over the fuselage. Good test requirements of FAR25.853, there are extended lifetime.
fewer material choices A systems design approach involves
for the radiant panel developing materials that exhibit a balance
FAR25.856 test. between flammability, acoustic performance,
The typical noise level in durability and weight. For example, the
the economy section of a mechanism of a sound barrier involves blocking a
commercial aircraft is about sound wave by virtue of its mass at the surface
75 dBA Speech Interference area, measured in terms of areal density. This
Level (SIL). A variety of implies that a heavier barrier material will reflect
materials have been sound better. However, in order to minimise fuel
developed to meet the needs costs, weight restrictions are frequently enforced
of this noise level on for all engineered materials. From a materials
commercial aircraft. The perspective this involves formulating a silicone
systems design approach, polymer with cross-functional ingredients that
using isolation and barrier exhibit synergistic effects between flammability
materials, typically improves and durability.
noise levels to 65 dBA SIL Rogers Corporation recently launched a new
or better. product family for vibration and acoustic
Acoustic insulation for mitigation called the BISCO® L3 Series. The
cabin noise reduction is next generation, BISCO L3 Sound Barrier, is an
located between the aircraft engineered, filled silicone rubber with extremely
skin and the interior side low flammability designed as an acoustic noise
panels. For improved barrier (mass layer) to meet the needs of the
performance a noise aircraft industry. This material will be available for
blocking layer (mass layer), any application that requires extremely low
such as a flame retardant flammability, smoke and toxicity.
silicone rubber, is used in a Aircraft interior designers can rely on BISCO
composite commonly Silicones to help them meet their vibration or
referred to as “insulation acoustic needs. These dissipative materials
blankets.” This material acts (foams, rubbers and composites) come in a
as a noise barrier by virtue of variety of thickness, areal densities and sizes
its mass, and it must meet allowing design flexibility.
Federal Aviation Regulations
for aircraft insulation See us on Stand 5G58
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