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COMPOSITE NOISE BARRIERS IN DEVELOPMENT OF STEEL COMPOSITE NOISE BARRIERS IN HIGHWAYS PRESENTED BY : FEBIN T S S7 MECHANICAL ROLL NO : 4430

INTRODUCTION Development of steel composite noise barrier due to the growing consciousness of noise pollution. To reduce noise level by 5 to 25 dB from 70 to 90dB on busy roads and highways. Appropriate design, acoustic performance and cost of prototype.

MECHANISM OF NOISE PROPOGATION Noise propagates through either solid, liquid or gas. Presence of barrier reflects, diffracts and transmits sound energy without following a direct path. Sharp or multiple edges of a barrier diffract or split sound waves and reduce intensity.

SOUND TRANSMISSION LOSS OF VARIOUS MATERIALS Thickness (mm) Surface Density (kg/m2) Transmission Loss (dB) Concrete 100 244 40 Brick 150 288 Steel 1.27 9.8 25 Aluminium 1.59 4.4 23 Wood 18 21 Plywood 16.1

WORKING OF NOISE BARRIER

SCHEMATIC DIAGRAM OF ABSORPTIVE PANEL GLASS FIBER MAT WRAPPED IN NYLON COLD FORMED GALVANISED SHEET SLOTTED GALVANISED SHEET TRAPEZOIDAL RIBS ON BACK PLATE SCHEMATIC DIAGRAM OF ABSORPTIVE PANEL BACK

PROTOTYPE BARRIER

ACOUSTIC MATERIALS Absorbing materials (porous): glass wool, open cell polyurethane foam. Barrier materials (heavy): metal, stone, glass etc. A higher mass of which leads to higher transmission loss of noise. Damping materials: felt and thermocol dampen structural vibration to prevent resonance.

DESIGN CONSIDERATIONS Acoustic considerations based on existing and desired noise levels in the protected area. Height depends on desired shadow zone. The bottom portion (around 1.8m above ground) is made of absorptive panels. Wind load and structural rigidity.

DESIGN CONSIDERATIONS Transparent panels are used to permit ingress of light. Reflective panels at higher elevations. To maximize performance to cost ratio total height of barrier varies between 2.8 to3.2m. Parallel reflective barriers width to height ratio of roadway to barriers should be at least 10:1,to avoid reduction in performance due to multiple reflections.

MATERIAL FOR NOISE BARRIER Reinforcement – glass fiber which are silica based and contains oxides of Ca, B, Na, Al, Fe etc. Reinforcement can be in the form of particles, whiskers, continuous fibers or sheets. Composite materials have fibrous reinforcement as its more stronger and stiffer than any other form

COMPOSITION OF PANEL Continuous glass fiber is used as reinforcement. Core of panels is filled with glass fiber, wrapped in nylon net which provides excellent sound absorbing capacity. Cold formed galvanized sheets have been used to provide structural rigidity and to possess better transmission loss.

NOISE BARRIERS USED ABROAD

APPLICATIONS Railway tracks in metro cities. Railway switchyards, bridges and tunnels. Airport terminals and boundaries. Enclosures for noisy equipments.

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