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ACOUSTICAL MATERIAL
SUBMITTED BY:
Rewa Marathe
Pallavi Chitnis
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Need for acoustical treatments goes back to Greek,since when they started using amphitheatres. Back inthose days these were achieved using brass vesselsfilled with water or other methods of similar kind.Now we have come a far way from those water filledbrass vessels. Today we use latest technology and
material to achieve desired acoustical effect. They are used for treating rooms with special
audibility requirements like auditoriums, movietheatres, amphitheatres, seminar halls, conferencerooms, recording rooms, etc.
Classification of acoustical materials: Sound absorbent
Sound reflecting
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Various kinds of materials are available in market. They
are listed below:
ACOUSTICAL PLASTER
ACOUSTICAL TILES
COMPRESSED WOOD PARTICAL BOARD
MINERAL WOOL
STRAW BOARD
PERFORATED PLYWOOD
FIBRE BOARD
WOOD WOOL BOARD
FIBRE GLASS
CORK BOARD/TILES
ROCK WOOL AND GLASS WOOL
GYPSUM BOARDS
THERMOCOL AND CORK
CARPETS AND CURTAINS
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ACOUSTICAL EFFICIENCY It most important factor and is
expressed as absorption coefficient of any material..
MAINTENANCE After insulation, maintenance plays a very
important role. Material selected should have clean and
presentable appearance, capable of being washed and
renovated if required.
VERMIN AND ROT PROOF- Acoustical Material are applied
to serve for long period and therefore they must be free
from these defects.
RESISTANCE TO PHYSICAL IMPACT- they should posses
adequate abrasive strength snd should not be affectedby physical contact.
RESISTANCE TO MOISTURE- they should have sufficient
resistance to mositure, but they should not be used in
damp conditions.
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HEAT INSULATION- MATERIAL CHOICE CAN CUT DOWN AIR-
CONDITIONING AND WINTER HEATING TO QUITE AN
EXTENT.WHILE SELECTION OF A MATERIAL IT SHOULD BECONSIDERED WHETHER IT IS TO BE APPLIED ON CEILINGS
OR WALLS.
INCOMBUSTIBILITY-ACOUSTICAL MATERIAL SHOULD BE
RESISTANT TO FIRE . FLAME RETARDANTS SHOULD BE
RENDERED IN THE MATERIAL WHILE ITS MANUFACTURINGPROCESS,TO PROVIDE ADDITIONAL HEAT INSULATION
PROPERTY TO THE MATERIAL
WEIGHT-LIGHT ACOUSTICAL MATERIAL ARE MORE SAFE TO
USE,AS IT ADHERSE PROPERLY TO THE SURFACE TO BE
TREATED AND CAN ALSO SUSPEND EASILY. AESTHETIC APPEARANCE- THOUGH THIS PROPERTY IS NOT
REALLY VERY IMPORTANT,BUT IT IS PREFERRED IF GOOD
FINISHED SURFACE IS ACHIEVED, WITH ITS ACTUAL PURPOSE
OF INSTALLATION
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SOFTMATERIALS- MATERIALSHAVINGSUFFICIENTPOROSITYANDGOODABSORBINGPOWER; LIKEHAIRFELT,ASBESTOS,ROCKWOOL,GLASS
SILK,ETC.FALLUNDERTHISCATEGORY.
SEMI-HARDMATERIALS-MATERIALSABLETOWITHSTANDROUGH
HANDLINGLIKECANEFIBRE,MINERALWOOLBOARDSANDTILESFALL
UNDERTHISCATEGORY.ACOUSTICALPLASTERSARESEMIHARDMATERIALS, WHICHCANBEAPPLIEDLIKEORDINARYPLASTER,THOUGH
REQUIRESKILLEDLABOURSFORITSAPPLICATION.
HARDMATERIALS- HARDPOROUSMATERIALS,MADEPOROUSDURING
THEIRPROCESSOFMANUFACTURING,LIKEPRFORATEDPANELS,POROUS
TILES,ETC.FALLUNDERTHISCATEGORY.
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ACOUSTICAL PLASTERS AND SPRAYED ON MATERIALS.
PREFABRICATED BOARDS OR TILES.
COMPOSITE OR ASSEMBELED UNITS.
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Correct techniques and proper job conditions should
followed for application
No installation should be done when the building is
recessively cold, damp, hot or dry.
All plastering concrete and terrazzo work includinggrinding should be completed and then made dry.
All doors and windows should be in place ad glazed.
Poured or precast concrete and gypsum or similar roof
decks should be thoroughly dry.
Form oil should be removed before application.
All the precautions should be discussed with the
acoustical.
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Suspended ceilings are used for many purposes including
acoustical treatments in form of tiles and sheets.
Suspended acoustical ceilings serve to provide sound
absorption and the most useful surface in a room. They
help in reducing reverberant sound intensity within a
room.
Sound absorbing ceilings available in the market today.
Human activity in offices and large publics paces generates
noise resulting in reduced work efficiency. Acoustical
(sound absorbing) ceiling systems help in reducing build-up
of reverberant noise because
of their excellent sound absorbing properties. This leads to
a better
Working environment and reduced annoyance due to high
noise levels.
In selecting a suspended ceiling ,the designer needs to
weigh the and performance requirements.
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Ceilings systems are available in gypsum, coated steel and
coated aluminum. They available in a variety of designs
including lineal ceilings, I-in or lay-in tile and plank
ceilings and C-grid (band raster) ceilings. Metal ceiling as
remanufacture in d aluminum and steel with coil coated
powder coated finishes. All metal ceilings are available in
a perforated version for sound absorption, and are
designed to integrate the standard lighting fixtures air
diffusers and partitions .
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Sound absorption
The sound absorbing efficiency of material is designated byits sound
Absorption coefficient (a). This is usually measure and
reported in octave bands over the frequency range of 125-
4000Hz, together with the Noise Reduction Coefficient
(NRC), which is the average of the sound absorptioncoefficient 250,500,1000and 2000Hz. This enables
calculation of noise reduction or reverberation time.
The increasing use of hard finishes and stone/tile finishes
in offices requires the use of highly sound absorbent
ceilings. offer NRC values of 0.75 up to 1.05 for differentceiling types.
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Traditionally, whenever sound absorption is required,
perforated metal ceiling panels are backed with a sound
absorbing layer of mineral wool or fiber glass. The use of a
fibrous sound absorbing medium always has other draw back is.
These include the difficulty in working with the fibrous
materials because of skin irritation and the problem of fibers
letting loose in to the air stream in an air-conditioned
environment. This ceiling range comprises perforated panels
with an acoustic non woven factory applied to the rear of the
panels. Due to the controlled sound impedance of this
perforated panel, and with a backing air space (ceiling
plenum)the, provides excellent sound absorption properties
without the use of any fibrous material behind the perforated
panel.
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SOUNDTRANSMISSION LOSS
Sound transmission loss is a measurement of soundinsulation between one room and an other. Onemanufacture provide sound
Transmission loss values for ceiling tiles.This information is
of doubtful utility because ceiling tiles are supported ongrids and
Have penetration through them to accommodal tieghtfittings and air
conditioning diffusers The overall sound transmission lossof such a composite ceiling will be 10-20dB lower than the
transmission loss of the ceiling panel ort ile alone.Whendesigning for soundi nsulation between rooms, thepartitionseparating the rooms is of major concern. Toprevent flanking sound transmission through thesuspended ceiling,it is important that partitions do notStopat the ceiling,but are extendedRight upto the roofslababove. sound insulationBetween adjacentspaces.
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Acoustic Wedges: To achievefree-field conditions within an
acoustic test environment for the
measurement of radiated sound
power and directivity, the testing
area must be free fromreverberation, feedback and
resonance throughout the audible
frequency spectrum.
Adhesive
Baffles: Baffles are used formost any interior space in need
of quality acoustical control.
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Barriers/Composites/Foam
Viscoelastic-damping
Compound, a high-performance
viscoelastic-damping compound,
decreases the sound traveing to
adjacent rooms.
Ceiling Tiles pinta's ceiling tiles
add texture, style and color to
any interior while solving a wide
array of acoustical issues
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Ceiling Tile Noise
Barrier CompositeCeiling Tile Noise Barrier
Composite improves the
transmission loss abilityof existing acoustic
ceiling tiles.
Ceiling Grid System
System is offered in
colors that complementthe Hypalon coating or
natural finish ceiling tiles
as well as our metal
ceiling tiles.
http://www.illbruck-sonex.com/products_CeilingGridSystem.phphttp://www.pinta-acoustic.com/UserFiles/CEILING_TILE_NOISE_BARRIER_COMPOSITE_3_08(1).pdf8/13/2019 Rewa, Pallavi
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Noise Control Curtainscurtain products to produce an
effective and economical method of
noise reduction for a wide variety of
industrial applications.
Wall Panels pinta offers a variety of
wall panels to meet all your acoustic
challenges.
Pipe Lagging PROSPEC Pipe Lagging
combines non-reinforced barrier witha thick foam decoupler to reduce
the noise created by vibrating pipes.
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Building bye laws by MP CINEMA ACT, 1972
construction:
No cinema shall be constructed underneath or on top
of any other building.
No open space shall be allowed under the floor ofauditorium.
Height of tiers:
Where the first tier or balcony extends over any part
of auditorium and such tier or balcony shall not be less
than 10 feet.
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Entrance and exit:
Cinema shall have a road frontage on the public
thoroughfare upon which the site of such cinema
abuts, and in such frontage there shall be suitable
means of entrance and exits for public . In addition
entrances and exits shall be reserved for service in
case of emergency opening on two separate and
distinct passages shall not be less than 5 feet width.
Two separate exits not opening on the same
thoroughfare of public passage shall be provided from
stage and from auditorium floor. Each of such exits
shall not be less than 5 which between the leaves of
the door when open.
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Seating : No part of auditorium shall provide accommodation
exclusive of passage, as a higher scale than 20 persons
per100 square feet.
All seats in the hall shall be firmly secured to the floor.
Gangways : A clear passage or gangway shall be formed at the sides
and down the centre of the seating in every part of the
auditorium in such a manner that no seat shall be ten or
more feet distant from a passage.
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Doors: All doors for the use of public shall be at least 46 wide with
the clear.
All doors shall open outwards to lie finish with the outside ofthe wall.
Width of corridor No staircase, landing lobby, corridor or passage, not being an
internal passage, not an internal passage between rows ofseats, intended for use as exit shall be less than five feet wideand there shall be no recesses or projection in the wall.
Staircase: Treads should not be less than 11 inches wide and with risers of
not more than 6 inches high. No staircase shall have more thantwo flight of 15 steps without a turn.
Ventilation : The area of the window, door and ventilator opening shall not
be less than one fifth of the total floor area.
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Planning:
The following conditions must be taken care of whileplanning a theatre:
1. Every member of the audience should have anunobstructed view of the entire picture withoutvisual, physical, and picture distortion.
2. Resolution and luminance of the picture must besatisfactory.
3. The auditorium should be suitable for soundreproduction and should be distortion and
coloration free.
4. There should be a reasonable balance betweenscreen size , viewing condition, seating conditionand circulation requirement.
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The size and the position of the screen must
relate to the size and shape of the
auditorium.
The max. distance of seating from screen isrecommended as five times the width of the
screen.
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It shall be three times for the screen of 35mm projection.
It shall be 2.5 times for the screen of 70 mm projection.
The overall length of the rear seating should be 3 times
width of the screen, 2 times for 35 mm projection and 2.5
to 3 times for 70 mm projection. The first row of seats should notbe closer to the screen.
The angle formed with the horizontal by a line from the
top of the projected picture to eye of the viewer in the
front row seat, should not exceed 35o preferably 30o.
The distance of screen from the first row shall be 2/3 ofthe screen width.
The width of seat pattern should vary from 1 times the
widest projected picture at the row to 1.3 times at the
row farthest from the screen.
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The volume provided in the hall is such that each person is
provided a space for about 3.75 times to 4.5 cum per
person.
Ration of H: W: l is 1:2:3 for approximate 800- 1000.
The size depend upon the total seating capacity, shape ofauditorium depend upon the acoustical requirement.
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The rear wall may be straight or curved
The rear wall does not folow the line of
curvature of the last seating row
The difference in shape of auditorium thuslies in pattern of side wall. They may be
rectangular, parabolic and diverging for part
or full, surated and splayed.
Usually concave divergence is emploeyd nearthe stage with straight and rectangular sides
towards rear.
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The ceiling of auditorium for cinema is not
normally provided as a flat horizontal
surface, as this type of ceiling causes uneven
distribution of sound and creates flutter and
echoes. The ceilings are applicable for upto
400 people.
Splayed ceiling with splays rising towards
rear reinforces sound for the rear seats.
Ceilings are principally sound distribution
surface and need no sound absorbing
material if properly designed.
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The generally acceptable noise level inside the auditoriumfrom point of view of comfort , economy and otherpractical consideration shall be 30 to 40 db.
The recommended Rt is .35 to .55 seconds for 1500cum.
Acoustical conditions:
This depend on auditorium shape acoustical absorptioncharacteristics of surface and reverberation resulting fromthem.
Rectangular rooms with parallel floors and ceiling surfacesspecially if long and narrow give worst results.
The ideal is fan shaped auditorium which is also ideal forviewing conditions.
Decay conditions: The characteristics of decay curvature of cinema should be
such that with reflected sound waves is attenuated by not lessthan 15 db by comparison by direct sound.
For cinema theatre reflected sound path should not exceed thedirect path more than 15m.
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A multiplex with four Audis.
It has a capacity of 250 people in each audi.
Acoustical treatment has been done using tapestry, micron
wadding, gypboards, fibrecrete, and woodwool panels.
Treatment has been provided between the wall which iscommon between two Audis to avoid passage of sound
from one Audi to the other. This has been done by
providing cavity wall filled up with micron wadding an
alternative of glass wool.
The floor has been covered with black acoustical carpet.
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Sound source is situated is situated behind
the screen in form of three LCR speakers.
The first 3-4m of the side recieves max.
intensity of sound and thus is heavily treatedfor absorption. The rest is divided into three
equal parts and treated for reducing sound
intensity in direction from screen towards
the rear.
The ceiling is treated Gyp boards.
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