ADVANCED CONSTRUCTION

MATERIALSADVANCED CONSTRUCTIONacousTICAL MATERIALSACOUSTICAL MATERIALS USED IN CONSTRUCTION FOR ACOUSTRICAL TREATMENTAll building materials and surface treatments used in the construction of auditoriums have the capacity to absorb sound to a certain degree. TYPES OF ACOUSTIC MATERIAL ACC. TO THEIR PROPERTIES :Porous materials Acoustical plasters & sprayed on materials Acoustical blanketsCarpets and fabrics

Panel (or memberane) absorbersCavity (or helmholtz) resonaters Ndiviusual cavity resonatersPerforated panel resonatersSlit resonatersSpace absorbersVariable absorbers

POROUS MATERIALSPOROUS MATERIALS : Fibre boards , soft plasters , mineral wools , and isolation blanketsBASIC CHARACTERISTICS : These are cellular network of interlocking pores. Incident sound energy is converted to heat energy within the pores .The fraction of incident sound thus converted to heat absorbed , while the remainder , reduced in energy.

FIBRE BOARDSMINERAL WOOLSA GOOD ABSORBER ATTACHED TO A POOR INSULATOR (PLYWOOD IS USED) A GOOD ABSORBER ATTACHED TO A POOR INSULATOR (SOUND-INSULATOR IS USED)

ACOUSTICAL PLASTERS AND SPRAYED ON MATERIALSMATERIALS : Sprayed limpet abestos , zonolite , vermiculate , sound shield , glatex , dekoosto , etc.BASIC CHARACTERISTICS : These acustical finishes are mostlt used for noise reduction purposes & sometimes in auditoriums where any other acoustical treatment would be impractical because of the curved of irregular shape of the surface. They are applied in a semiplastic consistency , either by spray gun or by hand trowelling.

LIMPET ABESTOSZONOLITEAVERAGE ABSORPTION OF A ACOUSTICAL TILE

ACOUSTICAL (ISOLATION) BLANKETSMATERIALS : Rock wool , glass fibres , wood fibres , hair felt , etc. BASIC CHARACTERISTICS : These are used i varying thicknesses b/w 1 to 5 in. Their absorption increases wih thickness , particularly at low frequencies.Since acoustical blankets do not constitute aesthetically satisfactory finish , they are normally covered with a suitable type of perforated board , wood slats , fly screening etc.

ROCK WOOLWOOD FIBRE

GLASS FIBREEFFECT OF PAINT ON POROUS PREFABRICATED ACOUSTICAL UNITSCARPETS AND FABRICSBASIC CHARACTERISTICS : In addition to their traditional role as floor coverings , carpets are now being used as versatile acoustical materials because they absorb airbonr sound and noises within the room , they reduce and in some cases almost completely eliminate impact noises from above , they eliminate surface noises (shuffeling of feet , clicking of heels , moving of furniture).

CARPETSCARPETSOUND ABSORPTION PLYWOOD SPACED 3 IN. FROM WALL

PANEL (OR MEMBRANE) ABSORBERSBASIC CHARACTERISTICS : The non perforated panel , or membrane , absorbs represents the second group of sound-absorbing materials. Any impervious material installed on a solid backing but separated from it by an air space will act as a panel absorber and will vibrate when struck by sound waves. The flexural vibration of the panel will then absorb a certain amount of incident sound energy by converting it into heat energy.

TYPICAL INSTALLATION OG A PERFORATED RESONATOR

PANELS PLACED ON THE WALLSCAVITY RESONATORSBASIC CHARACTERISTICS : The cavity resonators , the third and last group of sound absorbents , consist of an enclosed body of air confined within rigid walls and connected by a narrow opening (called the neck) to the surrounding space ,, in which the sound waves travel.A cavity resonator absorbs maximum sound energy in a narrow region of the frequency band . an empty jar or bottle , as described in sec. 4.6 , also acts as a cavity resonator ; however it s maximum absorption is confined to a narrow frequency band ; that is , it is extremely selective in its absorption.

CAVITY RESONATORS CAN BE APPLIED As indiviusual unitsAs perforated panel resonatorsAs slit resonators

CAVITY RESONATOR INSTALLATIONINDIVIUSUAL CAVITY RESONATORIndividual cavity resonator a made of empty clay vessels of different sizes were used in medieval Scandinavian churches. Their effective absorption spread between 100 and 400 hz. Standard concrete blocks using a regular concrete mixture but with slotted cavities , called soundblox units , constitute a contemporary version of the cavity resonator.PERFORATED PANEL RESONATORPerforated panels , spaced away from a solid backing , provide a widely used practical application of the cavity resonator principle. They contain a large number of necks , constituting the perforation of the panel , thus functioning as an array of cavity resonators. He perforation are usually circular .The air space behind the perforation forms the undivided body of resonator , separated into bays by horizontal and vertical elements of the framing system.SLIT RESONATORIn designing auditoriums the desired acoustical effect can be accomplished by using relatively inexpensive isolation blankets along the room surfaces. Due to their porosity , isolation blankets need protection against abrasion. The popularity of slit resonators in the acoustical control of auditorium is due to the fact that they offer a wide choice for individual design , although they are more expensive than the commercial , sometimes monotonous standard acoustical materials. Slit-resonators absorbers , using cavity bricks , special cavity concrete blocks.

ALTERNATIVE SERIES OF WOOD SLATS SLIT RESONATORSPACE ABSORBERSMATERIALS : Space absorbers are made of perforated sheets (steel , aluminium , hardboard etc.) In the shape of panels , prisms , cubes , spheres , cylinders , or single or double conical shells and are generally filled or lined with sound-absorbing materials such as rock wool , glass wool etc.BASIC CHARACTERISTICS : When the regular boundary enclousers of an auditorium do not provide suitable or adequate area for conventional acoustical treatment , sound absorbing objects , called space absorbers or functional absorbers , can be suspended as indivisual units from the ceiling.

PERFORATED ALUMINIUM SHEETPERFORATED HARDBOARD SHEETPERFORATED STEEL SHEETS WITH DIFF DIFFERENT SIZESVARIABLE ABSORBERSBASIC CHARACTERISTICS : Several attempts to do so have been made in the past , particularly in radio studios , where a noticable change in the rt is a frquently necessary . for this purpose various sliding , hinged , movable , and rotataeble panels have been constructed that can expose either reflective or absorptive surfaces.

WORKING OF VARIABLE ABSORBERSCHEMATIC ILLUSTRATION OF VARIABTION ABSORBERS WHICH PROVIDE MEANS FOR ALTERING THE ABSORPTION AND THUS THE RTFIRE RESISTANT BOARDSAfire resistantmaterialis one that is designed to resistburningand withstandheat.

It is used in thebunker gearworn by fire-fightersto protect them from theflamesof a burning building.

Fireproofingis rendering something (structures, materials, etc.) Proof against fire, or incombustible; or material for use in making anything fire-proof.

It is a passive fire protectionmeasure.

An item classed as fireproof is resistant in specified circumstances, and may burn or be rendered inoperable by fire exceeding the intensity or duration that it is designed to withstand.

Calcium Silicate Boards

Calcium Silicate Boards are one of the largest selling building boards across the world.It is preferred over plaster boards due to the strength of the material & also the manufacturing process. It possesses some of the core properties that are not found in contemporary building materials.It is made with Silicate and Calcium materials as aggregates and strong cellulose fibre as reinforcing materials.

They have a stable crystalline structure.

Calcium Silicate Boardsofferedfinds use in reduction of heat through heat transfer process and can be made available in various sizes with high compressive strength that ensures it does not crack or shrink under high temperature.

100 % asbestos free, lightweight and non-combustible, offer superior architectural flexibility, non brittle that allows them to be nailed or planed, can be painted so as to provide for good finish.

Properties:

Thickness: 6 / 8 / 10 / 12 mmDensity: 900 950 kg/cm2Impact Strength: 1200 1700 J / m2 Flexural Strength: 5 6 N / mm2 (Transverse); 10 11 M / mm2 (Longitudinal)Moisture Content: 12 15 %Thermal Conductivity: 0.13 Kcal / hr m degCShrinkage Dimension: 0.1 0.2%Alkalinity: pH = 10Fire Propagation Index: 4.0

Perlite BoardsPerliteis anamorphousvolcanic glassthat has a relatively highwatercontent, typically formed by the hydration ofobsidian (a naturally occurringvolcanic glassformed as anextrusive igneous rock.). It occurs naturally and has the unusual property of greatly expanding when heated sufficiently. It is anindustrial mineral and a commercial product useful for its light weight after processing.

This type of board is made up of expanded granulated volcanic rock (perfite) and of cellulosic fibres held together by a binder.

Perlite is different from other volcanic glasses because when the crushed ore is heated to a suitable point in its softening range, it expands from 4 to 20 times its original volume.

Used for low-slope roofing systems, perlite insulation is manufactured as a rigid board that is composed of these expanded volcanic minerals combined with organic fibers and binders.

An asphalt emulsion is used to treat the top surface to inhibit the absorption of bitumen.

Perlite is compatible with bitumen and other adhesives, fire-resistant, dimensionally stable, and compatible with other roofing materials.

The boards are covered with a specific coating which prevents excessive absorption of asphalt at the time of its application. The board will withstand impact, but care must be taken when handling the boards because they can break easily. The thermal resistance of the insulation is stable, but it has a relatively low R-value. Typically, perlite is not used with ballasted, loose-laid membranes because the board will readily absorb moisture.

Properties:

- Density: 350-450kg/m3- Anti-bend intensity: 8Mpa- Compressive strength: 0.35-0.8Mpa- Thermal conductivity: 0.035-0.075W/(m. K)- Moisture content(%): 10- Wet expansion rate(%): 0.25- Fireproof limit: 0.6-2h- Fireproof temperature: 1300degree- Sound-absorption coefficient: 0.03-0.8Advantages:

- Natural, environmental-friendly, Non-toxic and no radioactivity.- Fireproof, anti-corrosion.- Light density with good insulation for heating & sound.Gypsum BoardsGypsumis a softsulphate mineralcomposed ofcalcium sulphate dihydrate, with thechemical formulaCaSO42H2O.

It can be used as afertilizer, and is the main constituent in many forms ofplasterand is widely mined.

Gypsum board is primarily used as a finish for walls and ceilings, and is known in construction asdrywall, sheetrock or plasterboard.

Drywall is a panel made ofgypsum plasterpressed between two thick sheets of paper. It is used to make interior walls and ceilings.

Different thickness and multiple layers of wallboard provide increased fire rating based on the time a specific wall assembly can withstand a standardized fire test. Oftenperlite, vermiculite andboric acidare added to improve fire resistance.

Advantages:

- Ease of installation- Fire resistance- Sound isolation- Durability- Economy- VersatilityEase of installation:

Gypsum board building systems are easy to install for several reasons. Gypsum board panels are relatively large compared to other materials.

They come in 48- and 54-inch wide sheets and in lengths of 8, 10, or 12 feet, so they quickly cover large wall and ceiling areas.

Gypsum board assemblies require only a few tools for their construction.

Gypsum board can be cut with either a utility knife or a variety of saws, and it can be attached with a variety of fasteners, including screws, nails, and staples.

It can also be adhesively attached to many substrates.

Gypsum board is a lightweight material. Two workers can easily handle most panels and cover large areas in very short time periods.

Gypsum board is easily finished using either a few hand tools or relatively modest machines.

Gypsum board installers can quickly learn most application techniques in a few hours

Fire Resistance:

Gypsum board is an excellent fire-resistive building material.

Its non combustible core contains nearly 21% chemically combined water, as described earlier, which, under high heat, is slowly released as steam.

Because steam will not exceed 100 degrees Celsius under normal atmospheric pressure, it very effectively retards the transfer of heat and the spread of fire.

Even after complete calcination, when all the water has been released from its core, gypsum board continues to serve as a heat-insulating barrier.

Moreover, tests conducted show that gypsum board has a low flame-spread index and a low smoke-density index.

When installed in combination with other materials in laboratory-tested wall and ceiling assemblies, gypsum board serves to effectively protect building elements from fire for prescribed time periods

Durability:Gypsum board is used to construct strong, high quality walls and ceilings that offer excellent dimensional stability and durability. Surfaces created using gypsum board are easily decorated and refinished.

Economy:Gypsum board is readily available and easy to apply. It is an inexpensive wall surfacing material that provides a fire resistant interior finish. Gypsum board building systems can generally be installed at significantly lower labor costs than most alternate systems.

Versatility:Gypsum board satisfies a wide range of architectural requirements for design. Ease of application, performance, ease of repair, availability, and its adaptability to all forms of decoration combine to make gypsum board unmatched by any other surfacing product.

Sound isolation:Gypsum board wall and ceilings systems effectively help control sound transmission and prevents the transfer of unwanted sound to adjoining areas. Vermiculite boardThey are natural, harmless, environmental, high organic innovatory materials.

It is a good heat insulating material.

It has a bad reputation because it is often mined in the same places as asbestos which contaminate the vermiculite.

It is stronger more durable and less expensive than most fiber board and can be cut n worked just like wood.

CHARACTERISTICS:

Fire proofHeat insulation Sound insulationMoisture absorbingInsecticide tolerance WeatherabilityHigh tension stressLightweightFine electrical insulationEnvironment friendly non toxic and disease freeFire-resistance ratingAfire-resistance ratingtypically means the duration for which apassive fire protectionsystemcan withstand a standard fire resistance test.

This can be quantified simply as a measure of time, or it may entail a host of other criteria, involving other evidence of functionality or fitness for purpose.

REFRENCESBOOK : ARCHITECTURAL ACOUSTICS BY LESLIE L. DOELLE

BOOK : CONCEPTS IN ARCHITECTURAL ACOUSTICS BY M. DAVID EGAN

BOOK : AUDITORIUM DESIGN (JNAFAU LIBRARY)

INTERNET : WIKIPEDIA