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Seminar
On
Acoustic Textiles
Presented by:
Md. Vaseem Chavhan(10210115)
M.Tech (Textile Engg. & Mgt.)
2010-2012
Department of Textile Technology
Dr. B R Ambedkar , NIT Jalandhar.
INTRODUCTION
The sound is important part of our life, on the other hand if it is
out of control it will create problem ,so we need a sound but in
control.
Generally wood , textiles and synthetic material are used for
this purpose. But the use of textiles for noise reduction is based
on two major advantages of these materials, namely low
production costs and small specific gravity.
Textile plays dual role aesthetic as well as functional. So it is
added advantage to use Textile as an acoustic.
 Out of textiles, Nonwoven are preferred to use as acoustic due
to its more porous structure ,more surface area and low cost of
production.
Use of Recyclable raw material further reduced down the cost
and like recycled PET.
Renewable material is based on two alternatives for the
production of ecologically friendly products and low production
costs .
From architectural point of view textile as an acoustic , good
knowledge of textile material is required to control sound.
ACOUSTICS,SOUND AND NOISE
Acoustics
Acoustics is defined as the scientific study of sound which includes
the effect of reflection, refraction, absorption, diffraction and
interference.
Sound
Sound is an alternation of pressure that propagates through an
elastic medium such as air which produces an auditory.
Noise
Noise is an unwanted sound
MECHANISM OF SOUND ABSORPTION
IN FIBROUS MATERIALS
Acoustic porous materials can
have porosity greater than 90%.
Common sound absorption
materials are open cell foam and
fiber.
Sound absorption is an energy
conversion process. The kinetic
energy of the sound (air) is
converted to heat energy when the
sound strikes the cells or fibers.
Altogether the reasons for the acoustic energy loss when sound
passes through sound absorbing materials are due to
I. Frictional losses- owing to sound pressure, air molecules
oscillate in the interstices of the porous material with the
frequency of the exciting sound wave. This oscillation
results in frictional losses
II. Momentum losses- A change in the flow direction of
sound waves, together with expansion and contraction
phenomenon of flow through irregular pores, results in a
loss of momentum
III. Temperature fluctuations Owing to exciting of sound, air
molecules in the pores undergo periodic compression and
relaxation. This results in change of temperature
Theory of Sound Transmission Loss
Consider a homogeneous isotropic medium placed in the path of a
sound wave, whose pressure p(x) depends upon the time t and on
distance x
The wave amplitude decays (as a result of energy loss) with distance
by a factor e-αx then the sound pressure will depend upon the time
and the distance in accord with the general equation for a damped
sine wave is derived.
The general wave
equation:
(∂2 p/ ∂ x2) =
1/constant (∂2ρ / ∂ t2)
propagating in the air
filled pores of the
porous material.
The Wave Equation and The Attenuation Constant
1.Equation of continuity
Consider the motion of a fluid having no sources or sinks, that is,
there are no points at which fluid is produced or disappears, (the
concept of the fluid state includes gases), through a small
rectangular parallelepiped
ρ0 (∂ Vs/ ∂ x) = -h(∂ρ / ∂ t).. (i)
as the equation of continuity
Where
h- porosity of parallelepiped
2.Equation of state
The functional relation between pressure, volume (density), and
temperature of a body is termed the equation of state, and is one of
the most important relationship describing its thermal properties.
The fabric can be treated as a mixture of fibres and air.
ρ= ρ0 [1 + k(p/po)] as the equation of state (ii)
Where
Let ρ0 represent the average density of the air in
the volume V
and
let Vs represent the average velocity of the fluid
particles entering, the fluid density ρ.
where k is the ratio of specific heat at constant
pressure
Q is rate of flow of heat in Z direction
3.Equation of Motion
Fig – Motion of fluid through volume element
Considering pA is the total force applied and U the average
velocity of particle
-(∂ p/ ∂ x) = Yr+ j Yi U as the equation of motion (iii)
Attenuating Constant
Using above equations the attenuating constant is found out
α= { (wkh/2po) [-Yi + (Yi
2 + Yr
2)1/2] }1/2
where
U = the average velocity of particle
Vs = average velocity of fluid particle
w= 2π frequency
po = atmospheric pressure
h= porosity
k= 1.4
Yi and Y r = f (h, w, R, ρ )
ρ1= density of air
ρ2 = density of fibre
The acoustic transmission loss as a result of the fabric being
present in the sound path can be computed with the help of this
constant, using the expression:
Transmission Loss = 8.69 ∆x . α
where:
∆x = thickness of the fabric.
α -attenuating constant
Influence Of Fabric Parameters On Transmission Loss
(1) For a fabric of any parameters the transmission loss increases
with the frequency of the sound source.
(2) For a fabric of fixed thickness, air resistance and fibre density
the transmission loss increases with the weight per unit area of
the fabric.
(3) For a fabric of given weight per unit area, air resistance and
fibre density the transmission loss decreases with the thickness
of the fabric.
(4) For a fabric of given weight per unit area, thickness and fibre
density, the transmission loss increases with the air resistance of
the fabric.
(5) For a fabric of given weight per unit area and thickness, the
transmission loss decreases with the density of the fibre.
Essentially it can be concluded that any fabric parameter that
will change the microstructure of the fabric, regardless of
weight per unit area and thickness of the fabric, also will
change the transmission loss.
ABSORBENT MATERIAL
1.Porous Absorbers
All of these materials allow air to flow into clear structure
where sound energy is converted to heat.
 Porous absorbers are the most common ally used
absorbing materials.
Thickness plays an important role in sound absorption by
porous materials.
Common porous absorbers include carpet,
draperies, spray-applied cellulose, aerated
plaster, fibrous mineral wool and glass fiber,
open-cell, as shown in figure below
2.Panel absorbers
 Panel absorbers are non –rigid, on –porous materials which are
placed over an airspace that vibrates in a flexural mode in response
to sound pressure exerted by adjacent air molecules.
It is usually most efficient at absorbing low frequencies.
This fact has been placed in field on orchestra platforms here
thin wood paneling traps most of the bass ribbing the room
warmth.
Common panel absorbers include thin wood paneling over
framing, lightweight impervious ceiling and floors, glazing and
other large surfaces capable of resonating in response to sound.
3.Resonators
 Resonators typically act to absorb sound in a
narrow frequency range. Resonators include some
perforated materials and materials that have
opening (holes and slots).
The resonant frequency is governed by the size
of the opening, the length of neck and the volume
of air trapped in the chamber.
Long narrow air distribution slots in rooms for
acoustic music production should be viewed with
suspicion since the slots may absorb valuable low
–frequency energy.
4.Smart Absorbing Materials
More recently, the use of active noise control has been combined
with passive control to develop hybrid sound absorbers.
Active control technologies appear to be the only way to attenuate
the low-frequency noise components.
Therefore, a hybrid passive/ active absorber can absorb the incident
sound over a wide frequency range.
It shows the principle of such a device, which combines passive
absorbent properties of a porous layer and active control at its rear
face, where the controller can be implemented using digital
techniques.
Materials Coefficients
125Hz 250Hz 500Hz 1000Hz 2000Hz 4000Hz
Brick, unglazed, painted .01 .01 .02 .02 .02 .03
Carpet, heavy, on concrete .02 .06 .14 .37 .60 .65
Same, on 40oz hairfelt or foam rubber .08 .24 .57 .69 .71 .73
Concrete Block, light, porous .36 .44 .31 .29 .39 .25
Fabrics:
Light Velour, 10oz per sq yd, hung straight, in
contact with wall
.03 .04 .11 .17 .24 .35
Medium Velour, 14oz per sq yd, draped to half area .07 .31 .49 .75 .70 .60
Heavy Velour, 18-oz per sq yd, draped to half area .14 .35 .55 .72 .70 .65
Floor:
Concrete or Terrazzo .01 .01 .015 .02 .02 .02
Linoleum, asphalt, rubber, or cork tile on concrete .02 .03 .03 .03 .03 .02
Wood .15 .11 .10 .07 .06 .07
Wood parquet in asphalt on concrete .04 .04 .07 .06 .06 .07
Glass:
Large panes of heavy plate glass .18 .06 .04 .03 .02 .02
Marble or glazed tile .01 .01 .01 .01 .02 .02
Plaster, gypsum, or lime, rough finish on lath .14 .10 .06 .05 .04 .03
Plywood Paneling, 3/8-inch thick .28 .22 .17 .09 .10 .11
Open doors and windows 1.00 1.00 1.00 1.00 1.00 1.00
Sound Absorption Coefficients of some Material
ACOUSTIC MEASUREMENTS
The ability of the acoustic material to absorb the incident sound
wave can be evaluated by comparing the sound power levels
between the reflected sound wave and the incident sound wave.
Acoustic Measurements Methods
Measurement techniques used to characterize the sound absorptive properties of a
material are as below:
Reverberant Field Method for measuring sound absorption is concerned with
the performance of a material exposed to a randomly incident sound wave,
which technically occurs when the material is in diffusive field .
Impedance Tube Method uses plane sound waves that strike the material
straight and so the sound absorption coefficient is called normal incidence sound
absorption coefficient, NAC .
Steady State Method. This method is mostly used when the other will not work.
This particular method is described in ASTM E336‐71. To measure the
transmission coefficient of the materials, a third microphone or even a second
pair of microphone can be placed behind the test sample in a second impedance
tube.
Acoustical properties of fabric materials are measured by
one of two methods:
1. The impedance tube method (ASTM C 384-98)
2. The acoustical chamber method.
The impedance tube method uses very small test
samples.
Large reverberation rooms and large test samples are
used for the acoustic chamber method
The measurement of sound absorption of the ACF non –
woven is based on the method of ASTM E 1050
Acoustic Test for Fabric Material
The measurement of sound absorption of the ACF non –woven
is based on the method of ASTM E 1050
Standard test method for impedance and absorption of
Acoustics Properties using a tube ,Two microphone and a Digital
Frequency Analysis system as shown in figure
FACTORS INFLUENCING SOUND
ABSORPTION OF NONWOVEN
1.Fibre parameter
Fibre Type
The variations in sound reduction due to samples variety are
quite different .
The performance as an acoustic is changes with incidence
sound frequency
The average sound reduction
varies in the following order of
fabric samples:
P1>C2>C4>C1>C3>PP>P2>V>P3
The results with respect to these nine
nonwoven samples of polyester(P),
cotton(C), viscose(V) and 123 represent
different GSM and air permeability.
Fiber Size
Sound absorption coefficient depends upon fiber diameter. This is
because, thin fibers can move more easily than thick fibers on sound
waves.
A study showed that fine denier fibers ranging from 1.5 to 6
denier per filament (dpf) perform better acoustically than coarse
denier fibers.
At the same time micro denier fibers (less than 1 dpf) provide a
dramatic increase in acoustical performance.
Fiber Surface Area and Cross section
The friction between fibers and air increases with fiber surface
area resulting in a higher sound absorption.
The sound absorption in porous material is due to the viscosity
of air pressure in the pores or the friction of pore wall.
Therefore, sound absorption increases with specific surface
area of fiber with increase of relative density and friction.
Cross-section
The cross section of fibre which is giving more surface area is
preferred.
FIGURE 2. (a) 4DG, (b) trilobal, and (c) round fiber cross-sections.
4DG fiber has deep groves and channels along its longitudinal
axis. These grooves provide higher fiber surface area and hence the
better acoustic property
4DG fibers had approximately three times more surface area than
round fibers.
The decibel (dB) is a logarithmic unit that indicates the ratio of a physical quantity (usually power or intensity) relative to a specifiedor implied
reference level. A ratio in decibels is ten times the logarithm to base 10 of the ratio of two power quantities. A decibel is one tenth of a bel, a
seldom-used unit
Porous fibre
Samples produced with highpercentage of hollow fibers
recorded the highest rates of sound absorption, whereas samples
produced with100% polyester fibers recorded the lowest rates.
Sample produced using 55% polyester/45% hollow polyester
fibers and 600 g/m2, displayed the best results.
2.Fabric parameter
Airflow Resistance
One of the most important qualities that influence the sound
absorbing characteristics of a nonwoven material is the specific flow
resistance per unit thickness of the material.
In general, when sound enters these materials, its amplitude is
decreased by friction as the waves try to move through the tortuous
passages.
Porosity
Number, size and type of pores are the important for the sound
absorption mechanism in porous materials. This means, there
should be enough pores on the surface of the material for the
sound to pass through and get dampened.
Tortuosity
Tortuosity is a measure of the pores or streamline curvature.
Tortuosity describes the influence of the internal structure of
a material on its acoustical properties. It has also been said by
the value of tortuosity determines the high frequency
behavior of sound absorbing porous materials.
Thickness
The sound absorption in porous materials have concluded that
low frequency sound absorption has direct relationship with
thickness.
The rule of thumb rule that has been followed is the effective
sound absorption of a porous absorber is achieved when the
material thickness is about one tenth of the wavelength of the
incident sound
Density
Density of a material is often considered to be the important
factor that governs the sound absorption behavior of the material.
At the same time, cost of an acoustical material is directly related
to its density.
Less dense and more open structure absorbs sound of low
frequencies (500 Hz). Denser structure performs better for
frequencies above than 2000 Hz.
As indicated in Figure,
needle punched nonwoven
fabrics with higher
densities yielded better
sound insulation properties
than nonwoven fabrics at
lower densities
Orientation of web
Nonwoven composed with multi-angle layered web and different
thickness
Web orientation effects were analyzed through the nonwoven
composed of the same fibre contents, but with different
orientation angles (0°, 35°, 45° and 90°), manufactured and
controlled during the carding process.
The nonwoven’s absorber which has
an un-oriented web in the middle
layer has a higher NAC than
nonwovens which have a totally
oriented web structure, but the
difference is marginal.
Coating and Insertion(Panels)
In the case of coating structure, the panel promotes the NAC in
low- and middle-frequency regions, but it has the reverse effect
in the high frequency region by the coincidence effect. Therefore,
many considerations are required for the purpose of sound
control
On the other hand, the inserted panel structure contributed to
an increase in the NAC through all frequencies, because the
reflected sound wave inside the nonwoven sound
Fig Effect of panel vibration on sound
absorption properties
(COM-1 TO COM-3 Coated Samples with PP,
COM4 TOCOM-6 inserted samples)
The Effect Of Low Melting-Point Polyester Contents
 Roughly, the increase of the low melting point polyester
contents caused the NAC to decrease (visible especially within
the range 2000-3500Hz) because of the decrease in the
nonwoven thickness and the effect of the coincident effect.
Low melting-point polyester was used for bonding and better
strength.
The melted low melting-point
polyester fibre inside the
nonwoven caused a decrease in
nonwoven thickness and made
the structure in the web shrink
during the bonding process,
which also resulted in the
destruction of the micro-pore of
the nonwoven structure.
3.Placement / Position of Sound Absorptive Materials
Sound absorption of a material also depends on the position
and placement of that material is placed.
 In rectangular rooms it has been demonstrated that absorbing
material placed near corners and along edges of room surfaces is
most effective.
In speech studios, some absorbents that are effective at higher
audio frequencies should be applied at head height on the walls.
In fact, material applied to the lower portions of high walls can
be as much as twice as effective as the same material placed
elsewhere.
THE TEXTILE FORM OF SOUND
(ARCHITECTURAL DESIGN CONCEPT)
Two main questions arise from architectural basis
•How sound can be shaped by textile ?
•Conversely how textiles can be shaped by sound?
How Sound Can Be Shaped By Textile ( POSITION IS NOT FIX)
That textile is a good sound regulating material is a well
known phenomenon. However, there is another very
important factor which is determining the acoustic effect of
the textile. This is the shape and location in space.
Distance
The following two graphs are results of experiments with the
cotton weave. The first graph shows the importance of the
distance from the textile to the wall.
Five different distances, parallel to the wall were tested. An
optimal absorption is achieved by placing the textiles min.
50cm from the wall.
Figure . The graph shows the importance of the distance from the textile to the wall. The
photo shows frames with textile
•Textile is used most efficiently if it is completely unfolded and flat
Drape
•The second graph shows the importance of a draping of the
textile. With draping means that the fabric is pushed up like a
curtain.
•The 10m2 cotton canvas was first measured in plane mode, then
draped to half width, and finally to quarter width.
The graph shows the importance of the draping of the textile. The
photo shows frame with textile
How Can Sound Be Visualized In A Textile Form (Position is Fix)
•The question is about both the technique and the finished forms,
i.e. both about how to achieve the shapes and how shapes
appear.
•To apply this way of evaluating two principles are used:
First Design Principle
The first design principle focuses on the mathematics of sound.
This work combines 1) algorithmically derived cuts between the
layers, 2) the constraints of the laser cutting technique and 3) material
properties.
Figure. Alisa Andrasek´s algorithmic work Creature.
Second Design Principle
•The second design principle focuses on the visual form of
sound.
•To access this, the phenomenon of cymatics is studied. Cymatics
is the study of visual sound and vibration . Here sound vibrations
are visualized in a physical material, being solid, liquid, granular
or other.
Figure . Metal sheet with salt showing four Chladni figures and a graphic system of
Chladni figures (Left: MIT. Right: Chladni)
•An example is the
Chladni figures which
was actually a study of
how the frequency
could be determined by
the pattern formed on
a metal plate with salt
when a violin bow was
swept over the edge.
An acoustic textile
•An acoustic textile, however, must have acoustic properties in its
own. It must be specifically engineered to absorb sound. In general
terms, acoustic textiles fall in two classes of porous sound
absorber:
•Bulky, high-loft textiles, which essentially behave as a rigid,
porous sound absorber. such as fiberglass or mineral wool batts or
blankets, and needle punched, resin or thermally bonded fibrous
textiles.
•Light weight, compact woven and nonwoven textiles that behave
as porous screen. Such as Thin lightweight acoustic textiles, such
as INC Engineered Materials Deci-Tex range,
Specially used Acoustic Textile
 Vertically lapped nonwoven fabrics
 Recycled of pet sound-absorbing material
 Reinforced composite materials Basing on natural fibers
 Natural Fibre As a Acoustic Material
Vertically lapped nonwoven fabrics
•The different structures of the fibers result in different
total surface areas of nonwoven fabrics. Nonwoven fabrics
such as vertically lapped fabrics are ideal materials for use
as acoustical insulation products, because they have high
total surface.
• Vertically lapped nonwoven technology consists of
carding, perpendicular layering of the carded webs, and
through-air bonding using synthetic binder fibers.
•Further use of smaller deniers yield more fibers per unit
weight of the material, higher total fiber surface area, and
greater possibilities for a sound wave to interact with the
fibers in the fabric structure
A carding machine processes a properly mixed blend of
matrix and binder fibers (1). vibration Lapper (2) air thermal
bonding Chamber (3). cooled and wound up (4).
A simple layout of struto line and the position of fibers after
carding and struto processes
Recycled of pet sound-absorbing material
•PET resin recycled from other applications, such as from PET
beverage bottles or PET films, can be used to make the sound-
absorbing material by re melting the resin and using the fiber to
produce a nonwoven fabric.
•High-performance sound-absorbing materials have been
successfully developed using shaped PET fibers.
•Application of the newly developed materials to the dash
silencer and floor carpeting has improved sound insulation
performance while providing substantial weight reductions at
the same time.
•Compared with conventional materials, these newly
developed materials are easier to recycle, provide higher
quality and achieve superior levels of sound absorption and
insulation performance.
•In the case of high
frequency (f>1500 Hz), NAC
curves showed no clear
tendency with fine fibre
contents, but all the
samples have an
impressive sound
absorption rate.
Reinforced composite materials Basing on natural fibers
•Composite materials and layered structures basing on natural
plant fibers are increasingly regarded as an alternative to glass
fiber reinforced parts.
• One of their major field of application can be found in
structural components in the automotive industry.
•One of the main focus in the advancement of such products
is to achieve a maximum in driving comfort which in turn is
determined considerably by the interior acoustics of the
vehicle
•It was demonstrated that hybrid fleeces made of PP and natural
fibers have excellent characteristics regarding the
acoustical behavior
•Natural fiber composites containing flax/kenaf are
extensively used for many automotive molded products.
These show good thermal and acoustical insulation
properties as well.
•Cotton has properties comparable to these fibers and is a
suitable candidate except for its relatively high price.
•Recent studies have shown that cotton when combined
with flax or kenaf produces good molded products that have
acceptable physical properties and acoustical insulation
properties.
Environmental issues have been responsible for the growth of
natural fiber-based interiors over the past 5 years, and a further
gain in momentum appears to be underway in both Europe and
North America.
The natural fibre which are used as a acoustic are as follows
•Cotton
•Silk
•Hemp
•Wool
Natural Fibre As an Acoustic Material
Cotton
•Considering the lightweight, biodegradability and low cost of the
cotton raw material, the carbonized and activated cotton
nonwoven has a potential to be used as high-performance and
cost-effective acoustical materials.
•The study concluded that the activated carbon fiber nonwoven
ACF composite exhibited a greater ability to absorb normal
incidence sound waves than the composites with either glass fiber
or cotton fiber.
•The results showed that the nonwoven composites with cotton
as a surface layer had significantly higher sound absorption
coefficients than the glass fiber-surfaced composite in the
frequency range from 100 to 6400 Hz.
Recycled Cotton Acoustical Liner (QUIET LINER™)
Excellent Noise Absortion
•Class A Fire Rate
•Reduces Heat Loss/Gain
•No Formaldehyde
•Resists Microbial Growth
•Low Air Resistance
•No Itch or Skin Irritation
Quiet Natural Fiber Liner (Patent Pending) is a thermally bonded
HVAC insulation that offers superior acoustic and thermal
performance.
Silk for Curtain
•Silk weavers, have developed lightweight, translucent
curtain materials, which are excellent at absorbing sound.
This is a combination that has been lacking until now in
modern interior design.
•With a gap of 15 cm between curtain and wall, the new
developed curtain - depending on the frequency - absorbs up to
five times more sound than typical lightweight curtains.
Hemp
•Hemp fiber is naturally antimicrobial and resistant to ultraviolet
light, mold, mildew, and insects, which makes it of potential use
in outdoor applications.
•Evidently sound absorbing materials made of natural fibers such
as hemp can be recycled easily, and their production involves a
low carbon footprint and no CFC emissions, so that they can be
classified as ecologically green building materials.
•Studies have reported values of the
sound absorption coefficient of
hemp felt of different thicknesses.
Figure4shows the sound absorption
coefficient of material made of 80-
85% of hemp fibers.
Wool Carpet
“... carpet is one of the most practical and cost-effective products
available for controlling noise in the built environment.” Dianne
Williams,(Graeme E Harding and Associates, Consultants in Acoustics, Noise and Vibration )
•Wool carpet reduces airborne sound
•Wool carpet reduces surface noise
•Wool carpet reduces noise transmission
•Wool carpet provides superior acoustic insulation
The porosity of the surface of carpets means that sound waves
can penetrate into the pile, rather than being reflected back into
the room as they would from a smooth surface.
Carpets are extremely effective sound absorbers because the
individual fibers, pile tufts and underlay have different resonant
frequencies at which they absorb sound.
In this respect, wool carpets are particularly effective, as the
millions of wool fibers in an area of carpet have a range of lengths,
diameters, crimps and spirallity , which enables them to absorb
sounds over a wide range of frequencies
•Wool carpet reduces airborne sound
•Wool carpet reduces surface noise
Surface noise in a room is the sound from footsteps, dropped
objects and furniture movement.
Carpet reduces impact noise by over 20 dB(decibels), and also
ensures that the “life” of the noise is only half as long as that with
hard floorings . Again, the thicker the pile, the better the sound
reduction.
This type of noise control is particularly important in busy
restaurants and other locations where people need to be able to
communicate amidst a lot of activity creating a background of
continual impact sounds.
•Wool carpet reduces noise transmission
While carpets reduce noise transmission through the floor in
multi-storied buildings, the degree of actual noise reduction, as
well as people’s perception of it, are dependent on the frequency
distribution of the sound.
So again, wool carpet, because of the fibre’s natural ability to
absorb a wider range of frequencies, also provides superior sound
insulation for those below.
Carpet can improve the IIC (impact insulation class of common
flooring) ceiling systems by approximately 30 dB.
•Wool carpet provides superior acoustic insulation
Carpet’s multi-tasking abilities also mean that it can provide more
all-round acoustic performance than other floor coverings.
Trials under practical conditions have shown that the sound
absorbing efficiency of even heavily worn carpets was reduced by
no more than 16%, while after shampooing, which improves tuft
definition, the reduction was only 10% .
While acoustic ceiling panels absorb airborne sound, they do not
reduce surface impact noise. Therefore, in classrooms and other
such locations, where good sound reflection from the ceiling will
help project the teacher’s voice to the back of the class, wool
carpet will absorb or isolate other distracting impact noise
APPLICATION OF TEXTILE
SOUND ABSORPTIVE MATERIAL
Almost every textile has some potential for acoustic function.
In fact, textiles are used in many applications involving acoustics,
including:
•Acoustic panels
•Automotive
•Upholstery.
The acoustic as a panels used for decoration as well as
acoustic purpose, the different panel products used for
acoustic purpose as below
o PolyPhon Polyester Panels
o Acoustic Ceilings Systems
o 3D FabricPanels
o Visual Impact Acoustic Panels
o Quietspace™ Acoustic Fabric
•ACOUSTIC PANELS FOR WORKSTATIONS
Polyester Panels (PolyPhon)
Polyester Panels are a great choice for better sounding classrooms.
They have many advantages over other acoustical products
 The acoustical wall panels are made from 100% polyester (60%PET- recycled
fiber and 40% PET-virgin fiber) and are 100% recyclable
 Great Sound Absorption, NRC .75
 Cost effective and easy to install.
Acoustic Ceilings Systems
•Acoustic materials work to control the sound quality in a room by
controlling the absorption and diffusion of the sound waves.
•Suspended acoustic ceiling systems refer to acoustic panels or tiles
suspended by an exposed or concealed ceiling grid. The tiles
themselves can be made of fiberglass, mineral fiber, wood, or
metal.
•A suspended acoustic ceiling is a perfect example of an opportunity
to use acoustic textiles for broad-frequency sound absorption.
3D FabricPanels
•The panels are made in a modular style and covered in fabric
from Macquarie Fabrics to give a 3dimensional look on the wall.
• It is easy to install and reduce cost of installation.
Visual Impact Acoustic Panels With NETWORK Translucent Fabric
•Visual Impact Panels have been developed in conjunction
with Textile Mania to create an acoustic panel with a new unique
fabric.
•The panels are designed to be installed on walls or ceilings in
offices and public spaces to reduce reverberation and improve
sound quality.
•Network is translucent industrial mesh fabric with
excellent dimensional stability, that can be used for workstation
clamp on screens to control airflow, diffuse sound and provide
privacy.
•AUTOMOTIVE INSULATION
•Textiles are used in cars for a wide variety of purposes: to
enhance comfort, thermal insulation, design, vehicle safety and
more often for required acoustic properties.
•Acoustic protection is now recognized as a major contributor to
vehicle comfort and is no longer limited to the mere
soundproofing of the floor or engine.
•Textile composite used in cars refers to combination of one or
more textile and/or non-textile materials, e.g. foam and warp
knitted fabrics used as upholstery or interior trim materials.
•However, three-dimensional nonwovens are lately considered as
replacement for PUR foam. Some of the advantages of such
"textile foam" are: Reduced odours , uniformity , recycled fiber.
•A carpet is defined as "open" or as "closed", according to
the length of piles.
•The higher the values for the pile density and for frequency,
the higher the value for the absorption coefficient alpha will
be. In case tufted carpets, there are two distinct types of
yarn: the "endless" yarn and the staple fiber yarn.
•The staple fiber yarn has many fiber ends in the hank,
which enhance the volume and by this and by this the
absorption potential.
Floor carpet as a sound absorber
Roof paneling
In order to improve the absorption poten-tia1 of the roof
paneling, a two-layer PET construction would provide a solution:
on the visible side a PET nonwoven is lami-nated to an air-
permeable PET carpet bonded by thermal activated Bico/PET
fibers.
Seats
The car seats have large surface areas, and they even absorb
airborne noise in low frequency ranges, if covered with an air
permeable textile because of their thick molded upholstery.
Trunk
• A trunk should be constructed in a manner which prevents
the airborne noise (activated by the body) as far as possible
from entering the trunk and thus the interior.
•Extremely absorbent textile molded parts as well as textile
flat parts are installed to keep away any noise e.g. of the
exhaust system, from the rear passenger compartment
UPHOLSTERY IN CONCERT HALLS
Acoustical Noise Reduction Blankets
•The vinyl-coated facings on the noise reduction blankets
are dirt and oil resistant, cleanable and designed for high-
use industrial settings.
•The Audio Seal™ Acoustical Blankets offer a powerful
combination of noise reduction and durability.
•AQFA-10 Insulation Blankets offer strong sound
absorption via quilted fiberglass enclosed in heavy-duty
aluminized vinyl exterior.
Sound Absorbing Drapery (ACOUSTI-CURTAIN™)
•High Quality Construction
•PFR or IFR Face Layer & Lining Fabrics
•Excellent Sound Absorption
•Wool Core – Absorbs, Filters & Breaks Down Harmful VOC’s
From The Air
•Reflects Thermal Energy
CONCLUSION:
With increase in awareness and stander of living of people
the acoustic material having bright future.
 Particularly textile is best fit for this solution , due to its
performance and low cost of production also textiles act as a
dual role with decoration, cushion, upholstery etc. is also act as
acoustic.
Use of recyclable and eco friendly product for an acoustic
textile further confirm its position in market.
REFERENCES:
1. D. V. Parikh, Y. Chen and L. Sun,’ Reducing Automotive interior Noise with Natural Fiber
Nonwoven Floor Covering Systems’, Textile Research Journal Vol 761111 813-820.
2. Mevlut Tascan, ,‘ Effects of Fiber Denier, Fiber Cross-Sectional Shape and Fabric Density
on Acoustical Behavior of Vertically Lapped Nonwoven Fabrics’, Journal of Engineered
Fibers and Fabrics Volume 3, Issue 2—2008
3. Quietspace™ Acoustic Fabric, Product Specifications catalog .
4. Mahabir Singh Atwal,’ The Acoustic Properties Of Textile Fabrics ’ PhD Thesis, October
1982.
5. By Cecilie Bendixen, cand. Arch. Ph.D. candidate,’ The Textile Form Of Sound’, PhD Thesis.
6. Mevlut Tascan and Edward A. Vaughn, ‘Effects of Total Surface Area and Fabric Density on the
Acoustical Behavior of Needle punched Nonwoven Fabrics’ ,Textile Research Journal 2008; 78;
289.
7. Youneung Lee*, Changwhan Joo, ‘Sound Absorption Properties Of Recycled Polyesterfibrous
Assembly Absorbers’,’ AUTEX Research Journal, Vol. 3, No2, June 2003
8. http://www.physorg.com/news/2011-05-curtains-quench-noise.html
9. Mark Thomann, MHP – Stuart Jackson, LLC, ‘The Acoustical Properties of Wool Carpet’, Historic
Floor covring and Textile.
10. M D Teli, A Pal and Dipankar Roy, ‘Efficacy of nonwoven materials as sound insulator’, IJFTR ,
Vol. 32 June 2007, pg 202-206.
11. N. Jiang , J.Y. Chen , , D.V. Parikh, ‘Acoustical evaluation of carbonized and activated cotton
nonwovens’, Bioresource Technology 100 (2009) 6533–6536.
12. www.quietflex.com
13. Serenity Decorative Acoustic Panels , product catalog.
14. http://www.acousticalsurfaces.com/
15. Jorge P. Arenas, Malcolm J. Crocker, ‘Recent Trends in Porous
16. Sound-Absorbing Materials’, SOUND & VIBRATION/JULY 2010.
17. Abdelfattah, A. Mahmoud1, Ghalia E. Ibrahim and Eman R. Mahmoud2,’ Using
Nonwoven Hollow Fibers to Improve Cars Interior Acoustic Properties, Life Science
Journal, Volume 8, Issue 1, 2011.
18. Ching-Wen Lou, Jia-Horng Lin, And Kuan-Hua Su,’ Recycling Polyester and Polypropylene
Nonwoven Selvages to Produce Functional Sound Absorption Composites’, Textile Res. J.
75(5), 390–394 (2005)
19. Christian R. Koenig, Dieter H. Mueller, Acoustical properties of reinforced composite
materials basing on natural fibers, Document.
20. C.R. Koenig, D. H Muller and K D Thoben,’ Acoustic Parameters of Automotivre
Interior using hybrid flees basing on Natural Fibres’, Acoustics 08 Paris.
21. Ching-Wen Lou, Jia-Horng Lin, And Kuan-Hua Su,’ Recycling Polyester and Polypropylene
Nonwoven Selvages to Produce Functional Sound Absorption Composites’, Textile Res. J.
75(5), 390–394 (2005).
22. Cotton: Science and technology Edited by S. Gordon and Y-L. Hsieh. Woodhead Publishing
Limited ,Cambridge, England.
23. http://www.acousticalsurfaces.com/quiet_liner/quiet_liner.htm
24. http://www.acousticsblog.com/category/david-ingersoll.
25. www.textilemania.com.au
26. http://www.acousticalsurfaces.com/acoustical_drapery/acoustical_curtains.htm
27. "Curtains that 'quench' noise." PHYSorg.com. 3 May 2011. Page8
Thank You!
?

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Acoustic textiles (sound absorbing textile)

  • 1. Seminar On Acoustic Textiles Presented by: Md. Vaseem Chavhan(10210115) M.Tech (Textile Engg. & Mgt.) 2010-2012 Department of Textile Technology Dr. B R Ambedkar , NIT Jalandhar.
  • 2. INTRODUCTION The sound is important part of our life, on the other hand if it is out of control it will create problem ,so we need a sound but in control. Generally wood , textiles and synthetic material are used for this purpose. But the use of textiles for noise reduction is based on two major advantages of these materials, namely low production costs and small specific gravity. Textile plays dual role aesthetic as well as functional. So it is added advantage to use Textile as an acoustic.
  • 3.  Out of textiles, Nonwoven are preferred to use as acoustic due to its more porous structure ,more surface area and low cost of production. Use of Recyclable raw material further reduced down the cost and like recycled PET. Renewable material is based on two alternatives for the production of ecologically friendly products and low production costs . From architectural point of view textile as an acoustic , good knowledge of textile material is required to control sound.
  • 4. ACOUSTICS,SOUND AND NOISE Acoustics Acoustics is defined as the scientific study of sound which includes the effect of reflection, refraction, absorption, diffraction and interference. Sound Sound is an alternation of pressure that propagates through an elastic medium such as air which produces an auditory. Noise Noise is an unwanted sound
  • 5. MECHANISM OF SOUND ABSORPTION IN FIBROUS MATERIALS Acoustic porous materials can have porosity greater than 90%. Common sound absorption materials are open cell foam and fiber. Sound absorption is an energy conversion process. The kinetic energy of the sound (air) is converted to heat energy when the sound strikes the cells or fibers.
  • 6. Altogether the reasons for the acoustic energy loss when sound passes through sound absorbing materials are due to I. Frictional losses- owing to sound pressure, air molecules oscillate in the interstices of the porous material with the frequency of the exciting sound wave. This oscillation results in frictional losses II. Momentum losses- A change in the flow direction of sound waves, together with expansion and contraction phenomenon of flow through irregular pores, results in a loss of momentum III. Temperature fluctuations Owing to exciting of sound, air molecules in the pores undergo periodic compression and relaxation. This results in change of temperature
  • 7. Theory of Sound Transmission Loss Consider a homogeneous isotropic medium placed in the path of a sound wave, whose pressure p(x) depends upon the time t and on distance x The wave amplitude decays (as a result of energy loss) with distance by a factor e-αx then the sound pressure will depend upon the time and the distance in accord with the general equation for a damped sine wave is derived. The general wave equation: (∂2 p/ ∂ x2) = 1/constant (∂2ρ / ∂ t2) propagating in the air filled pores of the porous material.
  • 8. The Wave Equation and The Attenuation Constant 1.Equation of continuity Consider the motion of a fluid having no sources or sinks, that is, there are no points at which fluid is produced or disappears, (the concept of the fluid state includes gases), through a small rectangular parallelepiped ρ0 (∂ Vs/ ∂ x) = -h(∂ρ / ∂ t).. (i) as the equation of continuity Where h- porosity of parallelepiped
  • 9. 2.Equation of state The functional relation between pressure, volume (density), and temperature of a body is termed the equation of state, and is one of the most important relationship describing its thermal properties. The fabric can be treated as a mixture of fibres and air. ρ= ρ0 [1 + k(p/po)] as the equation of state (ii) Where Let ρ0 represent the average density of the air in the volume V and let Vs represent the average velocity of the fluid particles entering, the fluid density ρ. where k is the ratio of specific heat at constant pressure Q is rate of flow of heat in Z direction
  • 10. 3.Equation of Motion Fig – Motion of fluid through volume element Considering pA is the total force applied and U the average velocity of particle -(∂ p/ ∂ x) = Yr+ j Yi U as the equation of motion (iii)
  • 11. Attenuating Constant Using above equations the attenuating constant is found out α= { (wkh/2po) [-Yi + (Yi 2 + Yr 2)1/2] }1/2 where U = the average velocity of particle Vs = average velocity of fluid particle w= 2π frequency po = atmospheric pressure h= porosity k= 1.4 Yi and Y r = f (h, w, R, ρ ) ρ1= density of air ρ2 = density of fibre
  • 12. The acoustic transmission loss as a result of the fabric being present in the sound path can be computed with the help of this constant, using the expression: Transmission Loss = 8.69 ∆x . α where: ∆x = thickness of the fabric. α -attenuating constant
  • 13. Influence Of Fabric Parameters On Transmission Loss (1) For a fabric of any parameters the transmission loss increases with the frequency of the sound source. (2) For a fabric of fixed thickness, air resistance and fibre density the transmission loss increases with the weight per unit area of the fabric. (3) For a fabric of given weight per unit area, air resistance and fibre density the transmission loss decreases with the thickness of the fabric. (4) For a fabric of given weight per unit area, thickness and fibre density, the transmission loss increases with the air resistance of the fabric. (5) For a fabric of given weight per unit area and thickness, the transmission loss decreases with the density of the fibre. Essentially it can be concluded that any fabric parameter that will change the microstructure of the fabric, regardless of weight per unit area and thickness of the fabric, also will change the transmission loss.
  • 14. ABSORBENT MATERIAL 1.Porous Absorbers All of these materials allow air to flow into clear structure where sound energy is converted to heat.  Porous absorbers are the most common ally used absorbing materials. Thickness plays an important role in sound absorption by porous materials. Common porous absorbers include carpet, draperies, spray-applied cellulose, aerated plaster, fibrous mineral wool and glass fiber, open-cell, as shown in figure below
  • 15. 2.Panel absorbers  Panel absorbers are non –rigid, on –porous materials which are placed over an airspace that vibrates in a flexural mode in response to sound pressure exerted by adjacent air molecules. It is usually most efficient at absorbing low frequencies. This fact has been placed in field on orchestra platforms here thin wood paneling traps most of the bass ribbing the room warmth. Common panel absorbers include thin wood paneling over framing, lightweight impervious ceiling and floors, glazing and other large surfaces capable of resonating in response to sound.
  • 16. 3.Resonators  Resonators typically act to absorb sound in a narrow frequency range. Resonators include some perforated materials and materials that have opening (holes and slots). The resonant frequency is governed by the size of the opening, the length of neck and the volume of air trapped in the chamber. Long narrow air distribution slots in rooms for acoustic music production should be viewed with suspicion since the slots may absorb valuable low –frequency energy.
  • 17. 4.Smart Absorbing Materials More recently, the use of active noise control has been combined with passive control to develop hybrid sound absorbers. Active control technologies appear to be the only way to attenuate the low-frequency noise components. Therefore, a hybrid passive/ active absorber can absorb the incident sound over a wide frequency range. It shows the principle of such a device, which combines passive absorbent properties of a porous layer and active control at its rear face, where the controller can be implemented using digital techniques.
  • 18. Materials Coefficients 125Hz 250Hz 500Hz 1000Hz 2000Hz 4000Hz Brick, unglazed, painted .01 .01 .02 .02 .02 .03 Carpet, heavy, on concrete .02 .06 .14 .37 .60 .65 Same, on 40oz hairfelt or foam rubber .08 .24 .57 .69 .71 .73 Concrete Block, light, porous .36 .44 .31 .29 .39 .25 Fabrics: Light Velour, 10oz per sq yd, hung straight, in contact with wall .03 .04 .11 .17 .24 .35 Medium Velour, 14oz per sq yd, draped to half area .07 .31 .49 .75 .70 .60 Heavy Velour, 18-oz per sq yd, draped to half area .14 .35 .55 .72 .70 .65 Floor: Concrete or Terrazzo .01 .01 .015 .02 .02 .02 Linoleum, asphalt, rubber, or cork tile on concrete .02 .03 .03 .03 .03 .02 Wood .15 .11 .10 .07 .06 .07 Wood parquet in asphalt on concrete .04 .04 .07 .06 .06 .07 Glass: Large panes of heavy plate glass .18 .06 .04 .03 .02 .02 Marble or glazed tile .01 .01 .01 .01 .02 .02 Plaster, gypsum, or lime, rough finish on lath .14 .10 .06 .05 .04 .03 Plywood Paneling, 3/8-inch thick .28 .22 .17 .09 .10 .11 Open doors and windows 1.00 1.00 1.00 1.00 1.00 1.00 Sound Absorption Coefficients of some Material
  • 19. ACOUSTIC MEASUREMENTS The ability of the acoustic material to absorb the incident sound wave can be evaluated by comparing the sound power levels between the reflected sound wave and the incident sound wave.
  • 20. Acoustic Measurements Methods Measurement techniques used to characterize the sound absorptive properties of a material are as below: Reverberant Field Method for measuring sound absorption is concerned with the performance of a material exposed to a randomly incident sound wave, which technically occurs when the material is in diffusive field . Impedance Tube Method uses plane sound waves that strike the material straight and so the sound absorption coefficient is called normal incidence sound absorption coefficient, NAC . Steady State Method. This method is mostly used when the other will not work. This particular method is described in ASTM E336‐71. To measure the transmission coefficient of the materials, a third microphone or even a second pair of microphone can be placed behind the test sample in a second impedance tube.
  • 21. Acoustical properties of fabric materials are measured by one of two methods: 1. The impedance tube method (ASTM C 384-98) 2. The acoustical chamber method. The impedance tube method uses very small test samples. Large reverberation rooms and large test samples are used for the acoustic chamber method The measurement of sound absorption of the ACF non – woven is based on the method of ASTM E 1050 Acoustic Test for Fabric Material
  • 22. The measurement of sound absorption of the ACF non –woven is based on the method of ASTM E 1050 Standard test method for impedance and absorption of Acoustics Properties using a tube ,Two microphone and a Digital Frequency Analysis system as shown in figure
  • 24. 1.Fibre parameter Fibre Type The variations in sound reduction due to samples variety are quite different . The performance as an acoustic is changes with incidence sound frequency The average sound reduction varies in the following order of fabric samples: P1>C2>C4>C1>C3>PP>P2>V>P3 The results with respect to these nine nonwoven samples of polyester(P), cotton(C), viscose(V) and 123 represent different GSM and air permeability.
  • 25. Fiber Size Sound absorption coefficient depends upon fiber diameter. This is because, thin fibers can move more easily than thick fibers on sound waves. A study showed that fine denier fibers ranging from 1.5 to 6 denier per filament (dpf) perform better acoustically than coarse denier fibers. At the same time micro denier fibers (less than 1 dpf) provide a dramatic increase in acoustical performance.
  • 26. Fiber Surface Area and Cross section The friction between fibers and air increases with fiber surface area resulting in a higher sound absorption. The sound absorption in porous material is due to the viscosity of air pressure in the pores or the friction of pore wall. Therefore, sound absorption increases with specific surface area of fiber with increase of relative density and friction.
  • 27. Cross-section The cross section of fibre which is giving more surface area is preferred. FIGURE 2. (a) 4DG, (b) trilobal, and (c) round fiber cross-sections. 4DG fiber has deep groves and channels along its longitudinal axis. These grooves provide higher fiber surface area and hence the better acoustic property
  • 28. 4DG fibers had approximately three times more surface area than round fibers. The decibel (dB) is a logarithmic unit that indicates the ratio of a physical quantity (usually power or intensity) relative to a specifiedor implied reference level. A ratio in decibels is ten times the logarithm to base 10 of the ratio of two power quantities. A decibel is one tenth of a bel, a seldom-used unit
  • 29. Porous fibre Samples produced with highpercentage of hollow fibers recorded the highest rates of sound absorption, whereas samples produced with100% polyester fibers recorded the lowest rates. Sample produced using 55% polyester/45% hollow polyester fibers and 600 g/m2, displayed the best results.
  • 30. 2.Fabric parameter Airflow Resistance One of the most important qualities that influence the sound absorbing characteristics of a nonwoven material is the specific flow resistance per unit thickness of the material. In general, when sound enters these materials, its amplitude is decreased by friction as the waves try to move through the tortuous passages. Porosity Number, size and type of pores are the important for the sound absorption mechanism in porous materials. This means, there should be enough pores on the surface of the material for the sound to pass through and get dampened.
  • 31. Tortuosity Tortuosity is a measure of the pores or streamline curvature. Tortuosity describes the influence of the internal structure of a material on its acoustical properties. It has also been said by the value of tortuosity determines the high frequency behavior of sound absorbing porous materials. Thickness The sound absorption in porous materials have concluded that low frequency sound absorption has direct relationship with thickness. The rule of thumb rule that has been followed is the effective sound absorption of a porous absorber is achieved when the material thickness is about one tenth of the wavelength of the incident sound
  • 32. Density Density of a material is often considered to be the important factor that governs the sound absorption behavior of the material. At the same time, cost of an acoustical material is directly related to its density. Less dense and more open structure absorbs sound of low frequencies (500 Hz). Denser structure performs better for frequencies above than 2000 Hz. As indicated in Figure, needle punched nonwoven fabrics with higher densities yielded better sound insulation properties than nonwoven fabrics at lower densities
  • 33. Orientation of web Nonwoven composed with multi-angle layered web and different thickness Web orientation effects were analyzed through the nonwoven composed of the same fibre contents, but with different orientation angles (0°, 35°, 45° and 90°), manufactured and controlled during the carding process. The nonwoven’s absorber which has an un-oriented web in the middle layer has a higher NAC than nonwovens which have a totally oriented web structure, but the difference is marginal.
  • 34. Coating and Insertion(Panels) In the case of coating structure, the panel promotes the NAC in low- and middle-frequency regions, but it has the reverse effect in the high frequency region by the coincidence effect. Therefore, many considerations are required for the purpose of sound control On the other hand, the inserted panel structure contributed to an increase in the NAC through all frequencies, because the reflected sound wave inside the nonwoven sound Fig Effect of panel vibration on sound absorption properties (COM-1 TO COM-3 Coated Samples with PP, COM4 TOCOM-6 inserted samples)
  • 35. The Effect Of Low Melting-Point Polyester Contents  Roughly, the increase of the low melting point polyester contents caused the NAC to decrease (visible especially within the range 2000-3500Hz) because of the decrease in the nonwoven thickness and the effect of the coincident effect. Low melting-point polyester was used for bonding and better strength. The melted low melting-point polyester fibre inside the nonwoven caused a decrease in nonwoven thickness and made the structure in the web shrink during the bonding process, which also resulted in the destruction of the micro-pore of the nonwoven structure.
  • 36. 3.Placement / Position of Sound Absorptive Materials Sound absorption of a material also depends on the position and placement of that material is placed.  In rectangular rooms it has been demonstrated that absorbing material placed near corners and along edges of room surfaces is most effective. In speech studios, some absorbents that are effective at higher audio frequencies should be applied at head height on the walls. In fact, material applied to the lower portions of high walls can be as much as twice as effective as the same material placed elsewhere.
  • 37. THE TEXTILE FORM OF SOUND (ARCHITECTURAL DESIGN CONCEPT) Two main questions arise from architectural basis •How sound can be shaped by textile ? •Conversely how textiles can be shaped by sound?
  • 38. How Sound Can Be Shaped By Textile ( POSITION IS NOT FIX) That textile is a good sound regulating material is a well known phenomenon. However, there is another very important factor which is determining the acoustic effect of the textile. This is the shape and location in space.
  • 39. Distance The following two graphs are results of experiments with the cotton weave. The first graph shows the importance of the distance from the textile to the wall. Five different distances, parallel to the wall were tested. An optimal absorption is achieved by placing the textiles min. 50cm from the wall. Figure . The graph shows the importance of the distance from the textile to the wall. The photo shows frames with textile
  • 40. •Textile is used most efficiently if it is completely unfolded and flat Drape •The second graph shows the importance of a draping of the textile. With draping means that the fabric is pushed up like a curtain. •The 10m2 cotton canvas was first measured in plane mode, then draped to half width, and finally to quarter width. The graph shows the importance of the draping of the textile. The photo shows frame with textile
  • 41. How Can Sound Be Visualized In A Textile Form (Position is Fix) •The question is about both the technique and the finished forms, i.e. both about how to achieve the shapes and how shapes appear. •To apply this way of evaluating two principles are used: First Design Principle The first design principle focuses on the mathematics of sound. This work combines 1) algorithmically derived cuts between the layers, 2) the constraints of the laser cutting technique and 3) material properties. Figure. Alisa Andrasek´s algorithmic work Creature.
  • 42. Second Design Principle •The second design principle focuses on the visual form of sound. •To access this, the phenomenon of cymatics is studied. Cymatics is the study of visual sound and vibration . Here sound vibrations are visualized in a physical material, being solid, liquid, granular or other. Figure . Metal sheet with salt showing four Chladni figures and a graphic system of Chladni figures (Left: MIT. Right: Chladni) •An example is the Chladni figures which was actually a study of how the frequency could be determined by the pattern formed on a metal plate with salt when a violin bow was swept over the edge.
  • 43. An acoustic textile •An acoustic textile, however, must have acoustic properties in its own. It must be specifically engineered to absorb sound. In general terms, acoustic textiles fall in two classes of porous sound absorber: •Bulky, high-loft textiles, which essentially behave as a rigid, porous sound absorber. such as fiberglass or mineral wool batts or blankets, and needle punched, resin or thermally bonded fibrous textiles. •Light weight, compact woven and nonwoven textiles that behave as porous screen. Such as Thin lightweight acoustic textiles, such as INC Engineered Materials Deci-Tex range,
  • 44. Specially used Acoustic Textile  Vertically lapped nonwoven fabrics  Recycled of pet sound-absorbing material  Reinforced composite materials Basing on natural fibers  Natural Fibre As a Acoustic Material
  • 45. Vertically lapped nonwoven fabrics •The different structures of the fibers result in different total surface areas of nonwoven fabrics. Nonwoven fabrics such as vertically lapped fabrics are ideal materials for use as acoustical insulation products, because they have high total surface. • Vertically lapped nonwoven technology consists of carding, perpendicular layering of the carded webs, and through-air bonding using synthetic binder fibers. •Further use of smaller deniers yield more fibers per unit weight of the material, higher total fiber surface area, and greater possibilities for a sound wave to interact with the fibers in the fabric structure
  • 46. A carding machine processes a properly mixed blend of matrix and binder fibers (1). vibration Lapper (2) air thermal bonding Chamber (3). cooled and wound up (4). A simple layout of struto line and the position of fibers after carding and struto processes
  • 47. Recycled of pet sound-absorbing material •PET resin recycled from other applications, such as from PET beverage bottles or PET films, can be used to make the sound- absorbing material by re melting the resin and using the fiber to produce a nonwoven fabric. •High-performance sound-absorbing materials have been successfully developed using shaped PET fibers. •Application of the newly developed materials to the dash silencer and floor carpeting has improved sound insulation performance while providing substantial weight reductions at the same time.
  • 48. •Compared with conventional materials, these newly developed materials are easier to recycle, provide higher quality and achieve superior levels of sound absorption and insulation performance. •In the case of high frequency (f>1500 Hz), NAC curves showed no clear tendency with fine fibre contents, but all the samples have an impressive sound absorption rate.
  • 49. Reinforced composite materials Basing on natural fibers •Composite materials and layered structures basing on natural plant fibers are increasingly regarded as an alternative to glass fiber reinforced parts. • One of their major field of application can be found in structural components in the automotive industry. •One of the main focus in the advancement of such products is to achieve a maximum in driving comfort which in turn is determined considerably by the interior acoustics of the vehicle •It was demonstrated that hybrid fleeces made of PP and natural fibers have excellent characteristics regarding the acoustical behavior
  • 50. •Natural fiber composites containing flax/kenaf are extensively used for many automotive molded products. These show good thermal and acoustical insulation properties as well. •Cotton has properties comparable to these fibers and is a suitable candidate except for its relatively high price. •Recent studies have shown that cotton when combined with flax or kenaf produces good molded products that have acceptable physical properties and acoustical insulation properties.
  • 51. Environmental issues have been responsible for the growth of natural fiber-based interiors over the past 5 years, and a further gain in momentum appears to be underway in both Europe and North America. The natural fibre which are used as a acoustic are as follows •Cotton •Silk •Hemp •Wool Natural Fibre As an Acoustic Material
  • 52. Cotton •Considering the lightweight, biodegradability and low cost of the cotton raw material, the carbonized and activated cotton nonwoven has a potential to be used as high-performance and cost-effective acoustical materials. •The study concluded that the activated carbon fiber nonwoven ACF composite exhibited a greater ability to absorb normal incidence sound waves than the composites with either glass fiber or cotton fiber. •The results showed that the nonwoven composites with cotton as a surface layer had significantly higher sound absorption coefficients than the glass fiber-surfaced composite in the frequency range from 100 to 6400 Hz.
  • 53. Recycled Cotton Acoustical Liner (QUIET LINER™) Excellent Noise Absortion •Class A Fire Rate •Reduces Heat Loss/Gain •No Formaldehyde •Resists Microbial Growth •Low Air Resistance •No Itch or Skin Irritation Quiet Natural Fiber Liner (Patent Pending) is a thermally bonded HVAC insulation that offers superior acoustic and thermal performance.
  • 54. Silk for Curtain •Silk weavers, have developed lightweight, translucent curtain materials, which are excellent at absorbing sound. This is a combination that has been lacking until now in modern interior design. •With a gap of 15 cm between curtain and wall, the new developed curtain - depending on the frequency - absorbs up to five times more sound than typical lightweight curtains.
  • 55. Hemp •Hemp fiber is naturally antimicrobial and resistant to ultraviolet light, mold, mildew, and insects, which makes it of potential use in outdoor applications. •Evidently sound absorbing materials made of natural fibers such as hemp can be recycled easily, and their production involves a low carbon footprint and no CFC emissions, so that they can be classified as ecologically green building materials. •Studies have reported values of the sound absorption coefficient of hemp felt of different thicknesses. Figure4shows the sound absorption coefficient of material made of 80- 85% of hemp fibers.
  • 56. Wool Carpet “... carpet is one of the most practical and cost-effective products available for controlling noise in the built environment.” Dianne Williams,(Graeme E Harding and Associates, Consultants in Acoustics, Noise and Vibration ) •Wool carpet reduces airborne sound •Wool carpet reduces surface noise •Wool carpet reduces noise transmission •Wool carpet provides superior acoustic insulation
  • 57. The porosity of the surface of carpets means that sound waves can penetrate into the pile, rather than being reflected back into the room as they would from a smooth surface. Carpets are extremely effective sound absorbers because the individual fibers, pile tufts and underlay have different resonant frequencies at which they absorb sound. In this respect, wool carpets are particularly effective, as the millions of wool fibers in an area of carpet have a range of lengths, diameters, crimps and spirallity , which enables them to absorb sounds over a wide range of frequencies •Wool carpet reduces airborne sound
  • 58. •Wool carpet reduces surface noise Surface noise in a room is the sound from footsteps, dropped objects and furniture movement. Carpet reduces impact noise by over 20 dB(decibels), and also ensures that the “life” of the noise is only half as long as that with hard floorings . Again, the thicker the pile, the better the sound reduction. This type of noise control is particularly important in busy restaurants and other locations where people need to be able to communicate amidst a lot of activity creating a background of continual impact sounds.
  • 59. •Wool carpet reduces noise transmission While carpets reduce noise transmission through the floor in multi-storied buildings, the degree of actual noise reduction, as well as people’s perception of it, are dependent on the frequency distribution of the sound. So again, wool carpet, because of the fibre’s natural ability to absorb a wider range of frequencies, also provides superior sound insulation for those below. Carpet can improve the IIC (impact insulation class of common flooring) ceiling systems by approximately 30 dB.
  • 60. •Wool carpet provides superior acoustic insulation Carpet’s multi-tasking abilities also mean that it can provide more all-round acoustic performance than other floor coverings. Trials under practical conditions have shown that the sound absorbing efficiency of even heavily worn carpets was reduced by no more than 16%, while after shampooing, which improves tuft definition, the reduction was only 10% . While acoustic ceiling panels absorb airborne sound, they do not reduce surface impact noise. Therefore, in classrooms and other such locations, where good sound reflection from the ceiling will help project the teacher’s voice to the back of the class, wool carpet will absorb or isolate other distracting impact noise
  • 61. APPLICATION OF TEXTILE SOUND ABSORPTIVE MATERIAL Almost every textile has some potential for acoustic function. In fact, textiles are used in many applications involving acoustics, including: •Acoustic panels •Automotive •Upholstery.
  • 62. The acoustic as a panels used for decoration as well as acoustic purpose, the different panel products used for acoustic purpose as below o PolyPhon Polyester Panels o Acoustic Ceilings Systems o 3D FabricPanels o Visual Impact Acoustic Panels o Quietspace™ Acoustic Fabric •ACOUSTIC PANELS FOR WORKSTATIONS
  • 63. Polyester Panels (PolyPhon) Polyester Panels are a great choice for better sounding classrooms. They have many advantages over other acoustical products  The acoustical wall panels are made from 100% polyester (60%PET- recycled fiber and 40% PET-virgin fiber) and are 100% recyclable  Great Sound Absorption, NRC .75  Cost effective and easy to install.
  • 64. Acoustic Ceilings Systems •Acoustic materials work to control the sound quality in a room by controlling the absorption and diffusion of the sound waves. •Suspended acoustic ceiling systems refer to acoustic panels or tiles suspended by an exposed or concealed ceiling grid. The tiles themselves can be made of fiberglass, mineral fiber, wood, or metal. •A suspended acoustic ceiling is a perfect example of an opportunity to use acoustic textiles for broad-frequency sound absorption.
  • 65. 3D FabricPanels •The panels are made in a modular style and covered in fabric from Macquarie Fabrics to give a 3dimensional look on the wall. • It is easy to install and reduce cost of installation.
  • 66. Visual Impact Acoustic Panels With NETWORK Translucent Fabric •Visual Impact Panels have been developed in conjunction with Textile Mania to create an acoustic panel with a new unique fabric. •The panels are designed to be installed on walls or ceilings in offices and public spaces to reduce reverberation and improve sound quality. •Network is translucent industrial mesh fabric with excellent dimensional stability, that can be used for workstation clamp on screens to control airflow, diffuse sound and provide privacy.
  • 67. •AUTOMOTIVE INSULATION •Textiles are used in cars for a wide variety of purposes: to enhance comfort, thermal insulation, design, vehicle safety and more often for required acoustic properties. •Acoustic protection is now recognized as a major contributor to vehicle comfort and is no longer limited to the mere soundproofing of the floor or engine. •Textile composite used in cars refers to combination of one or more textile and/or non-textile materials, e.g. foam and warp knitted fabrics used as upholstery or interior trim materials. •However, three-dimensional nonwovens are lately considered as replacement for PUR foam. Some of the advantages of such "textile foam" are: Reduced odours , uniformity , recycled fiber.
  • 68. •A carpet is defined as "open" or as "closed", according to the length of piles. •The higher the values for the pile density and for frequency, the higher the value for the absorption coefficient alpha will be. In case tufted carpets, there are two distinct types of yarn: the "endless" yarn and the staple fiber yarn. •The staple fiber yarn has many fiber ends in the hank, which enhance the volume and by this and by this the absorption potential. Floor carpet as a sound absorber
  • 69. Roof paneling In order to improve the absorption poten-tia1 of the roof paneling, a two-layer PET construction would provide a solution: on the visible side a PET nonwoven is lami-nated to an air- permeable PET carpet bonded by thermal activated Bico/PET fibers. Seats The car seats have large surface areas, and they even absorb airborne noise in low frequency ranges, if covered with an air permeable textile because of their thick molded upholstery.
  • 70. Trunk • A trunk should be constructed in a manner which prevents the airborne noise (activated by the body) as far as possible from entering the trunk and thus the interior. •Extremely absorbent textile molded parts as well as textile flat parts are installed to keep away any noise e.g. of the exhaust system, from the rear passenger compartment
  • 71. UPHOLSTERY IN CONCERT HALLS Acoustical Noise Reduction Blankets •The vinyl-coated facings on the noise reduction blankets are dirt and oil resistant, cleanable and designed for high- use industrial settings. •The Audio Seal™ Acoustical Blankets offer a powerful combination of noise reduction and durability. •AQFA-10 Insulation Blankets offer strong sound absorption via quilted fiberglass enclosed in heavy-duty aluminized vinyl exterior.
  • 72. Sound Absorbing Drapery (ACOUSTI-CURTAIN™) •High Quality Construction •PFR or IFR Face Layer & Lining Fabrics •Excellent Sound Absorption •Wool Core – Absorbs, Filters & Breaks Down Harmful VOC’s From The Air •Reflects Thermal Energy
  • 73. CONCLUSION: With increase in awareness and stander of living of people the acoustic material having bright future.  Particularly textile is best fit for this solution , due to its performance and low cost of production also textiles act as a dual role with decoration, cushion, upholstery etc. is also act as acoustic. Use of recyclable and eco friendly product for an acoustic textile further confirm its position in market.
  • 74. REFERENCES: 1. D. V. Parikh, Y. Chen and L. Sun,’ Reducing Automotive interior Noise with Natural Fiber Nonwoven Floor Covering Systems’, Textile Research Journal Vol 761111 813-820. 2. Mevlut Tascan, ,‘ Effects of Fiber Denier, Fiber Cross-Sectional Shape and Fabric Density on Acoustical Behavior of Vertically Lapped Nonwoven Fabrics’, Journal of Engineered Fibers and Fabrics Volume 3, Issue 2—2008 3. Quietspace™ Acoustic Fabric, Product Specifications catalog . 4. Mahabir Singh Atwal,’ The Acoustic Properties Of Textile Fabrics ’ PhD Thesis, October 1982. 5. By Cecilie Bendixen, cand. Arch. Ph.D. candidate,’ The Textile Form Of Sound’, PhD Thesis. 6. Mevlut Tascan and Edward A. Vaughn, ‘Effects of Total Surface Area and Fabric Density on the Acoustical Behavior of Needle punched Nonwoven Fabrics’ ,Textile Research Journal 2008; 78; 289. 7. Youneung Lee*, Changwhan Joo, ‘Sound Absorption Properties Of Recycled Polyesterfibrous Assembly Absorbers’,’ AUTEX Research Journal, Vol. 3, No2, June 2003 8. http://www.physorg.com/news/2011-05-curtains-quench-noise.html 9. Mark Thomann, MHP – Stuart Jackson, LLC, ‘The Acoustical Properties of Wool Carpet’, Historic Floor covring and Textile. 10. M D Teli, A Pal and Dipankar Roy, ‘Efficacy of nonwoven materials as sound insulator’, IJFTR , Vol. 32 June 2007, pg 202-206. 11. N. Jiang , J.Y. Chen , , D.V. Parikh, ‘Acoustical evaluation of carbonized and activated cotton nonwovens’, Bioresource Technology 100 (2009) 6533–6536. 12. www.quietflex.com 13. Serenity Decorative Acoustic Panels , product catalog.
  • 75. 14. http://www.acousticalsurfaces.com/ 15. Jorge P. Arenas, Malcolm J. Crocker, ‘Recent Trends in Porous 16. Sound-Absorbing Materials’, SOUND & VIBRATION/JULY 2010. 17. Abdelfattah, A. Mahmoud1, Ghalia E. Ibrahim and Eman R. Mahmoud2,’ Using Nonwoven Hollow Fibers to Improve Cars Interior Acoustic Properties, Life Science Journal, Volume 8, Issue 1, 2011. 18. Ching-Wen Lou, Jia-Horng Lin, And Kuan-Hua Su,’ Recycling Polyester and Polypropylene Nonwoven Selvages to Produce Functional Sound Absorption Composites’, Textile Res. J. 75(5), 390–394 (2005) 19. Christian R. Koenig, Dieter H. Mueller, Acoustical properties of reinforced composite materials basing on natural fibers, Document. 20. C.R. Koenig, D. H Muller and K D Thoben,’ Acoustic Parameters of Automotivre Interior using hybrid flees basing on Natural Fibres’, Acoustics 08 Paris. 21. Ching-Wen Lou, Jia-Horng Lin, And Kuan-Hua Su,’ Recycling Polyester and Polypropylene Nonwoven Selvages to Produce Functional Sound Absorption Composites’, Textile Res. J. 75(5), 390–394 (2005). 22. Cotton: Science and technology Edited by S. Gordon and Y-L. Hsieh. Woodhead Publishing Limited ,Cambridge, England. 23. http://www.acousticalsurfaces.com/quiet_liner/quiet_liner.htm 24. http://www.acousticsblog.com/category/david-ingersoll. 25. www.textilemania.com.au 26. http://www.acousticalsurfaces.com/acoustical_drapery/acoustical_curtains.htm 27. "Curtains that 'quench' noise." PHYSorg.com. 3 May 2011. Page8
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