Architectural acoustics

1. Prepared by:
A M S thilAr. M. Senthil

3. Wavelength
The distance, measured in the direction of
propagation of a wave, from any point to the
next point of corresponding phase.

4. Transverse and longitudinal wavesTransverse and longitudinal waves
• In case of solids, these
simple harmonicsimple harmonic
vibrations(air particles
vibration) produce
transverse waves in which
the motion of thethe motion of the
individual particles are at
right angles to the motion
of the waves.
f l d d• In case of liquids and gases
, the waves produced are
longitudinal in which the
motion of the individual
i l ll l hparticles are parallel to the
motion of the waves.

5. Simple harmonic motionSimple harmonic motion
• In a simple harmonic wave motion
of sound, whether it is longitudinal
or transverse, particle repeatedly
attain maximum displacement in
iti d ti di ti tpositive and negative directions at
periodic distances.
• The number of times each particle
k th t d f timakes the to‐and‐fro motion
about its mean position is called
frequency, f, and the time taken
for one such motion is called thefor one such motion is called the
period ,t.
• Frequency f = 1 / t

6. Velocity of sound wavesVelocity of sound waves
• In case of a solid bar the velocity of theIn case of a solid bar , the velocity of the
sound v is given by v = E/ p
• Where E= Modulus of Elasticity• Where E= Modulus of Elasticity
• P = density of the material

7. Wave Characteristics
Wave Fronts
• One –Dimensional wave frontOne Dimensional wave front
• Two‐ Dimensional wave front
• Three‐Dimensional wave front
Wave Surfaces
Crests, Troughs, Condensation and Rarefactions
In a transverse wave motion the maximum and minimumIn a transverse wave motion, the maximum and minimum
displacements are called the crest and the trough in a
longitudinal wave motion the corresponding points of
maximum and minimum displacements are calledmaximum and minimum displacements are called
compressions and rarefactions

8. Properties of soundProperties of sound
• Characteristics of soundCharacteristics of sound
• Behaviour of sound in enclosures
fl i f d• Reflection of sound
• Echoes
• Dispersion
• Sound shadowsSound shadows

9. Characteristics of sound
The three characteristics of sound are
1. The Intensity(I) of sound: which refers to its y( )
loudness and depends on the amplitude of
the sound wave, Iα A².,
2. The Pitch of sound: which depends on the
frequency of the sound wavefrequency of the sound wave.
3. The Quality of sound: which distinguishes the
sound produced by one source from anothersound produced by one source from another.

10. Characteristics of sound
Sound travels in air with a velocity of 336 m/s atSound travels in air with a velocity of 336 m/s at
normal temperature and pressure.
There are two scales of measurement of soundThere are two scales of measurement of sound
level
1. Phone: It is a scale which takes into account the1. Phone: It is a scale which takes into account the
varying sensitivity of the ear to sounds of
different frequencies
2. Sones: It is a scale which gives the proportional
apparent loudness of sounds.

11. Behaviour of sound in enclosures
• When sound generated in a room it is reflected, absorbed
and transmitted in various proportions in accordance with
h f i Th f h b h ithe nature of construction. These aspects of the behavior
of sound are very important from the acoustical point of
view.

12. Reflection of sound
• Sound waves reflected at a convex surface areSound waves reflected at a convex surface are
bigger.
• Sound waves reflected at a concave surface• Sound waves reflected at a concave surface
are smaller.

13. Echoes
• Echoes can be distinguished when reflectedEchoes can be distinguished when reflected
sound is heard about one‐fifteenth of a
second or more after the direct soundsecond or more after the direct sound.

14. Dispersion
• Sound striking a modelled surface is broken upSound striking a modelled surface is broken up
into a number of small and weak waves. This
scattering effect can be used to preventscattering effect can be used to prevent
echoes.

15. Sound shadows
• When a sound wave is interrupted by an
obstruction, a sound shadow is formed behind it, , ,
similar to light shadows.
• Sound shadows are the areas of poor audibility. p y

16. Common Indoor and Outdoor Noise Levels

17. Permissible Noise Level Exposure
Background Noise level:
Usually, sounds which do not contain any meaningful information are
referred to as background noise (e.g. noise from air conditioning or g ( g g
traffic). The background noise level is measured in dB.

18. Sono meterSono meter
• A Sonometer is an apparatus made of a hollow box having two holes. A
string is attached to it by which the transverse vibrations of strings can be
studied. One end of the string is fixed and the other end it is attached to a
pulley with a weight holder below the pulley .
• Weights can be added to the holder to produce tension in the wire.
• A sonometer demonstrates the relationship between frequency of
the sound produced by a plucked string, and the tension, length and mass
per unit length of the string. These relationships are usually
called Mersenne’s laws after Marin Mersenne(1588–1648), who
investigated and codified them .

19. SonometerSonometer
For small amplitude vibration, the frequency is proportional to:
• The square root of the tension of the string,
• The reciprocal of the square root of the linear density of the string,
• The reciprocal of the length of the string

20. Sound Absorption coefficient(α)Sound Absorption coefficient(α)
• The sound absorption coefficient α describes the property of a material to
convert incident sound into other forms of energy – e.g. thermal or kinetic
energy – and thus to absorb it.
• The sound absorption coefficient α of a material indicates the amount of
the absorbed portion of the total incident sound. α = 0 means that no
absorption occurs; the entire incident sound is reflected. If α = 0.5, 50 % of
the sound energy is absorbed and 50 % is reflected. If α = 1, the entire
incident sound is absorbed, there is no longer any reflection.

21. Absorption coefficientAbsorption coefficient
• The sound absorption coefficient of a material is α = (1 − r), where r, the sound
energy reflection coefficient, is the ratio of sound energy reflected from the
f f h i l h i id isurface of the material to that incident upon it.

22. Resonance Absorber
Resonance Absorber: This term comprises allResonance Absorber: This term comprises all
types of absorbers using a resonance
mechanism such as an enclosed air volume ormechanism such as an enclosed air volume or
a vibrating surface. Resonance absorbers are
mainly suitable for absorbing sound ofmainly suitable for absorbing sound of
medium to low frequencies.

23. Reverberation time
• The reverberation time is the basis for ratings of room acoustic quality.
The following table provides an overview of the typical reverberation times of
different room types.

24. Reverberation time
• The reverberation time depends mainly on three factors:
‐ the volume of the room,
‐ the surfaces of the room andthe surfaces of the room and
‐ the furniture in the room.
• A room usually becomes more reverberant with increasing height.
Absorbing surfaces – such as carpets, curtains and sound absorbing bso b g su aces suc as ca pe s, cu a s a d sou d abso b g
ceilings, but also furniture or people present in the room – reduce the
reverberation time.
• The reverberation time of a room can be derived from the calculated total
equivalent sound absorption area using the Sabine formula.
• Sabine formula: T= 0.163 X V/A
T – Reverberation time
V – Volume of the room
A – Total equivalent sound absorption area

25. NoiseNoise
Every day we encounter sounds that annoy us, that interfere with our
hearing and communication, or that may be hazardous to our
health. Any such unwanted sounds are called noise.This can be observed in
i t ll i ki i tprivate as well as in working environments.

26. Types of NoiseTypes of Noise
There are four types of noise:e e a e ou types o o se:
❑ Continuous :Noise is continuous if the
magnitude of the noise does not vary over time.g y
❑ Intermittent :Noise is intermittent if the noise
stops and starts at intervals.
❑ Impulsive :Noise is impulsive if the noise is large
in magnitude but short in duration.
❑ Varying: Noise is varying if the magnitude of the
noise changes over time.

27. Noise TransmissionNoise Transmission
• When a sound wave impacts upon the surface of a solid body, p p y,
some portion of it's energy will be reflected, some absorbed
and the rest transmitted through the body. The relative
proportion of each depends on the nature of the materialproportion of each depends on the nature of the material
impacted.

28. Transmission of NoiseTransmission of Noise
Noise emitted from a source is transmitted through many complicated paths, g y p p ,
sometimes through a conductor and sometimes as radiation. When it reaches a
device or equipment, that equipment is exposed to noise.

29. Transmission Loss (TL)Transmission Loss (TL)
• Transmission Loss
• If we consider the transmission of sound through a partition, we
can actually measure the sound energy on both the source side
(Wsrc) and the receiving side (Wrec) to determine exactly what
fraction of the sound is transmitted through We can thusfraction of the sound is transmitted through. We can thus
determine the transmission coefficient (t) for that partition as
follows:
• t = Wreceiver/Wsource
• The term Transmission Loss (TL), or more commonly Sound ( ), y
Reduction Index (SRI) are used to describe the reduction in sound
level resulting from transmission through a material. This is given
by:
• SRI 10 log (Wsource / Wreceiver) 10 log (1/t) 10 log (t)• SRI = 10 log (Wsource / Wreceiver) = 10 log (1/t) = ‐10 log (t)

30. Transmission Loss (TL)
A measurement of how much
sound energy is reduced in
transmission through materials.

31. Sound Transmission Loss of some
typical Building Elementstypical Building Elements

32. Noise controlNoise control
To approach the solution to any specific noise problem, we
need to:
1. Understand the basic physics of acoustics and how noise —
unwanted sound — is produced, how it propagates, and
how it is controlled.
2. Learn the basics of noise control, and how to approach the
problem from three standpoints: the source of noise, the
path it travels, and the point of reception.
3. Become familiar with, and discover how to apply in both
new and remodeling construction, the acoustical products g p
and systems that control noise — products that contribute
to the creation of acoustically comfortable, productive, and
healthful environments.

33. Noise controlNoise control
Three ways to control noise
There are only three basic ways to attenuate or reduce sound, whether at the source,
at the listener’s location, or along the path it travels from the source to the
receiver:
1 R l th d ith i t1. Replace the sound source with a quieter one.
2. Block the sound with a solid, heavy material that resists the transmission of sound
waves.
3 Absorb the sound with a light porous material that soaks up sound waves3. Absorb the sound with a light, porous material that soaks up sound waves.

34. Controlling noise at the source
Before designing acoustical treatment to attenuate noise at the source,
consider the following measuresconsider the following measures:
1. Moving the source to a more distant location or to another area, where its
noise will not reach an
objectionable level at the listener’s place.j p
2. Adjusting or modifying the source for quieter operation. If for example the
source of noise is a mechanism such as a fan or motor, it may be operated
at a lower speed.
3 Repairing or servicing the noise source It may be as simple a matter as3. Repairing or servicing the noise source. It may be as simple a matter as
lubricating gears, tensioning drive belts, or tightening loose and vibrating
screws or bolts.
4. Mounting the noise source on a resilient base (such as springs or soft pads)
i l ib i d h d h b d i ito isolate vibration and thus reduce the structure borne sound arriving at
the listener’s location.
5. Replacing the noise source with a quieter one. Modern appliances, for
example, generally operate much more quietly than older models.p , g y p q y

35. Controlling noise along its pathControlling noise along its path
• Reflected sound may be reduced by placing sound absorbing y y p g g
materials on surfaces from which sound will be reflected.

36. Controlling noise at the receiverControlling noise at the receiver
• If source control is not practical, another approach would be to treat the
problem at the receiver.
• “Temporary” sound control: Direct ear protection (earplugs or earmuffs)
is often used to protect workers’ hearing when source and path noise
control are not practical or possible.

37. Acoustics
Fundamentals

38. Acoustics
is usually very broadly defined as "the science of
sound."
Room Acoustics
The shaping and equipping of an enclosed space top g q pp g p
obtain the best possible conditions for faithful hearing
of wanted sound and the direction and the reduction of
unwanted soundunwanted sound.
Room Acoustics deal primarily with the control of sound
which originates within a single enclosure, rather than
its transmission between rooms.

39. frequency;frequency;
vibration cycles per second
amplitude
wave length:
distance between identical points on a wave

40. Speaker
diameter
(cm)
Frequencies
(Hz)
cutoff
ka(cm) (Hz) ka
Woofer 30 20-2,000 5.5
mid-mid
range
12 2,000-5,000 5.5
tweeter 6
5,000-
5 5tweeter 6
10,000
5.5
super-
tweeter
3
10,000-
20 000
5.5
The human ear can detect sounds between
tweeter 20,000
The human ear can detect sounds between
20 HZ and 20,000 HZ.
Most sensitive in the range of 100HZ to 5000HZMost sensitive in the range of 100HZ to 5000HZ
Hear it: http://www.surendranath.org/Applets.html , then select: menu/ new
applets/new menu/ waves/ hear the beats.

41. The length of a sound wave
20,000 HZ ‐ 11/16”
20 HZ – 56 ½ feet

42. Velocityy
Rate at which sound travels through a conductor
Air:
Wood:
Steel:

43. Velocityy
Rate at which sound travels through a conductor
Air: 1128 feet per second
Wood: 11,700 feet per second
Steel: 18,000 feet per second

44. Sound Pressure/
Amplitude

45. The Mobility of Sound

46. Direct Sound
Since sound travels in all directions from the source,
each listener will hear just the segment if the overall
d th t i t li i di t li t hisound wave that is traveling in a direct line to his
hear (in a space free from reflecting surfaces). As the
distance from the source increases, the sound,
pressure at the listener's ear will decrease
proportionately.
(Example: good Headphones)

47. Reflection

48. DiffusionDiffusion

49. Diffraction: The Sound Squeezes Through
Sound waves are not always reflected or absorbed.
When an obstacle is the same size as the wavelength
or less the sound can bend around obstacles or flowor less, the sound can bend around obstacles or flow
through small openings, and continue onward. This is
called diffraction. This action is more likely for deeper
d ( f l f d h h lsounds (of low frequency, and this with longer
waveforms).

50. ReverberationReverberation
The perpetuation of reflected sound within a space after theThe perpetuation of reflected sound within a space after theThe perpetuation of reflected sound within a space after theThe perpetuation of reflected sound within a space after the
source has ceased is calledsource has ceased is called reverberationreverberation. The time interval. The time interval
between reflections is usually so short that distinct echoesbetween reflections is usually so short that distinct echoes
are not heard Instead this series of reflections will blendare not heard Instead this series of reflections will blendare not heard. Instead, this series of reflections will blendare not heard. Instead, this series of reflections will blend
with the direct sound to add "depth". Reverberation is awith the direct sound to add "depth". Reverberation is a
basic acoustic property of a room. It can enrich speech andbasic acoustic property of a room. It can enrich speech and
i i lli i ll it l h d tit l h d tmusic in all areasmusic in all areas ---- or it can slur speech and generateor it can slur speech and generate
higher noise levels throughout a room, depending upon thehigher noise levels throughout a room, depending upon the
room volume, timing, and absorption.room volume, timing, and absorption.

51. Room Acoustics Volume
Shape
MaterialsMaterials
Room Acoustics

52. Reflect
Room Acoustics
Reflect
Absorb
Sound re‐enforcement

53. Th h fThe shape of a space
determines the sound
path within the space

54. Room Acoustics
C
B
AAAA
Reverberation

55. P ll l fl tiParallel reflective
surfaces generates g
unwanted
b ireverberation

56. Reverberation time must
match room functionmatch room function
•Pure speech requires short
reverberation time
•Symphony blends notes with long•Symphony blends notes with long
reverberation time

57. Studies based on the audibility of speech and music
l th t th t d i bl b tireveal that the most desirable reverberation
times generally fall within the ranges shown below.
These values are based on a sound frequency of 500
H ( i t it h f l h)Hz (approximate pitch of male speech).
Reverberation time in seconds
Speech
ffSmall offices 0.50 to 0.75
Classrooms/lecture rooms 0.75 to 1.00
Work rooms 1.00 to 2.00
Music
Rehearsal rooms 0.80 to 1.00
Chamber music 1.00 to 1.50
Orchestral/Choral/
Average church music 1.50 to 2.00g
Large organ/liturgical choir 2.00 to 2.25

58. Absorbing Materials
•Carpet
•Soft ceiling tile•Soft ceiling tile
•Rigid foam
•people

59. R fl ti M t i lReflecting Materials
•Masonry•Masonry
•Wood – smooth panels
•Smooth concrete
•Glass

60. Live
Auditoriums, theaters
(for music)
Obtain proper reverberation time to enhance musical
quality.quality.
Provide reflective surfaces near source to reinforce
sound; absorptive surfaces toward rear.
Medium Live
Conference and board rooms
Normal speech must be heard over distances up to about
35 ft.
Allow middle section of ceiling to act as a reinforcingAllow middle section of ceiling to act as a reinforcing
sound-reflector. Apply absorbent to periphery of ceiling or
to wall surfaces (not both). Additional treatment will
t ib t littl t i d ticontribute little to noise reduction.

61. MediumMedium
Cafeterias (school or office)
R d ll i l lReduce overall noise level.
Use highly sound-absorptive ceiling; also use quiet
equipment such as rubberized dish trays.q p y
Gymnasiums
Instructor must be heard over background noiseInstructor must be heard over background noise
Use acoustical material over entire ceiling to reduce
noise; walls remain untreated to permit some
fl t d dreflected sound.

62. Medium DeadMedium Dead
Elementary-grade classrooms
Teacher must be heard distinctly; reduce noise levelTeacher must be heard distinctly; reduce noise level
produced by children.
Acoustical ceiling essential. Supplementary acoustical
space units on upper rear and side walls are desirablespace units on upper rear and side walls are desirable.
Music rehearsal rooms
Unlike music hall instructor must hear individual notesUnlike music hall, instructor must hear individual notes
distinctly; minimum reverberation desired.
Entire ceiling, sidewalls, and wall facing musicians would
b t t d ll b hi d i i b l ft dbe treated; wall behind musicians may be left sound-
reflective for proper hearing. Room should be located
away from normal use rooms.

63. Dead
Kindergarten
Maximum noise reduction.
Maximum acoustical treatment on ceiling; space unitsg; p
on available wall surfaces.
Vocational classrooms and shopsVocational classrooms and shops
Maximum noise reduction.
Acoustical tile or lay-in panel ceiling, plus acoustical
f il bl ll ltreatment of available upper wall areas; locate away
from normal use rooms.

64. Reverberation time (in seconds) =Reverberation time (in seconds) =
.05 x volume of room
______________________________
bisabins

65. Sabin
The amount of sound absorbed is measured in
sabins One sabin is equal to the soundsabins. One sabin is equal to the sound
absorption of one square foot of perfectly
absorptive surface. The sound absorptionp p
equivalent to an open window of one square
foot. (theoretical, since no such surface exists).

66. Measuring Absorption:g p
Sound Absorption Coefficient
The fraction of the energy absorbed (at a
specific frequency) during each reflection is
represented by the sound absorptionrepresented by the sound absorption
coefficient of the reflecting/absorbing surface.
In the building industry, this is a meaningfulIn the building industry, this is a meaningful
and widely accepted quantitative measuring
of sound absorption, and applies to all
surfaces -- whether they be of reflective or
absorptive materials.

67. Reflective SurfacesReflective Surfaces
Hard, massive, non-porous surfaces, such as, , p ,
plaster, masonry, glass and concrete, absorb
generally less than 5% of the energy of
iki d d fl hstriking sound waves and reflect the rest.
Such materials heaver absorption coefficients
of 05 or lessof .05 or less.

68. Absorptive Surfaces:
Porous materials such as acoustical tile,
carpets draperies and furniture are primarilycarpets, draperies and furniture are primarily
absorptive. They permit the penetration of
sound waves and are capable of absorbingp g
most of the sound energy. These materials
may have absorption coefficients approaching
1 00 (one sabin per sq ft )1.00 (one sabin per sq. ft.).

69. Poor acoustical characteristics in this lecture room.

70. Reflective surfaces near the speaker.Reflective surfaces near the speaker.
In lecture rooms more than 40 feet long, the rear wall
should be absorptive to prevent echoes.

71. Background NoiseBackground Noise

72. Acceptable Background Noise Levelsp g
As a rule, we can tolerate, and even welcome, a
certain amount of continuous sound before itcertain amount of continuous sound before it
becomes noise. An "acceptable" level neither disturbs
room occupants nor interferes with the
communication of wanted sound.
Recommended category classification and suggestedRecommended category classification and suggested
noise criteria range for steady background noise as
heard in various indoor functional activity areas as
indicated in the Preferred Noise Criterion
(PNC)Curves.

73. Type of Space (and acoustical requirements)
PNC curve
Concert halls opera houses and recital halls (for listening toConcert halls, opera houses, and recital halls (for listening to
faint musical sounds)
10 to 20 db
Large auditoriums, large drama theaters, and churches (forLarge auditoriums, large drama theaters, and churches (for
excellent listening conditions)
Not to exceed 20 db
Broadcast, television, and recording studios (close microphone
pickup only)
Not to exceed 25 db
Small auditoriums, small theaters, small churches, musical
h l l ti d f (frehearsal rooms, large meeting and conference rooms (for
good listening), or executive offices and conference rooms for
50 people (no amplification)
Not to exceed 35 dbNot to exceed 35 db
Bedrooms, sleeping quarters, hospitals, residences,
apartments, hotels, motels, etc. (for sleeping resting, relaxing)
25 to 40 db25 to 40 db
Private or semiprivate offices, small conference rooms,
classrooms, libraries, etc. (for good listening conditions)
30 to 40 db

74. Type of Space (and acoustical requirements)
PNC curve
Living rooms and similar spaces in dwellings (for
conversing or listening to radio and TV)
30 to 40 db30 to 40 db
Large offices, reception areas, retail shops and stores,
cafeterias, restaurants, etc. (for moderately good listening
conditions)conditions)
35 to 45 db
Lobbies, laboratory work spaces, drafting and engineering
rooms, general secretarial areas (for fair listening, g ( g
conditions)
40 to 50 db
Light maintenance shops, office and computer equipment
rooms, kitchens and laundries (for moderately fair listening
conditions)
45 to 55 db
L l b PNC 60 t d d f ffiLevels above PNC-60 are not recommended for any office
or communication situation.

75. Minimize Background Noise Level - Overallg
noise levels which may interfere with wanted communication should
always be anticipated and corrected. To provide maximum quiet,
typical methods include the following:yp g
1. Elimination of outside noise by sound attenuation in walls,
ceilings, and floor
2. Use of quiet mechanical equipment wherever possible.
3 Control of remaining noise by absorption carpeting upholstery3 .Control of remaining noise by absorption -- carpeting, upholstery,
and acoustical treatment placed above and behind audience.
4 Individual handling of unusual noise sources -- for example4. Individual handling of unusual noise sources -- for example,
isolation of a noisy movie projector.
5. Electronic amplification of the wanted sound level above the5. Electronic amplification of the wanted sound level above the
background noise level -- usually done as a last resort.

76. Masking:
Creating Background "Noise“
When an undesirable background sound can't be
reduced or eliminated, it can sometimes be masked
(made less objectionable by introducing a different
sound). For example, piped-in music in restaurants can
mask the din of dish clatter and multiple conversation.p
At the other extreme, a masking sound may be
introduced to correct an oppressively quiet room. For
example, a telephone ring or a slight cough can bep , p g g g
distracting in a very "dead" room, and speech privacy
would be impossible. In many cases the heating and
air conditioning systems will provide a sufficientair conditioning systems will provide a sufficient
amount of masking noise.

77. Sound IsolationSound Isolation

78. The control of intruding sound ideally begins with the initial building
concept and continues to be a consideration through the life of the
building Total sound conditioning affectsbuilding. Total sound conditioning affects
1. site selection
2 b ildi i i h i2. building orientation on the site
3. room orientation within the building
4. design, detailing, specification
5. construction5. construction
6. inspection.
Predictable sound attenuation can be achieved by careful attention toPredictable sound attenuation can be achieved by careful attention to
detail during all phases of planning and construction.

79. Site Selection for Sound Control
Orientation

80. Room Arrangement
1. What is the STC rating of the outside kitchen exterior wall?

81. sound barrier

82. Sound BarriersSound Barriers
If the noise source is intense and no natural sound
barrier exists, a man-made sound barrier should be
considered as part of the design. A solid fence-type
barrier may remove from 10 to 20 db from the noise
level High-frequency sounds will be reduce morelevel. High frequency sounds will be reduce more
than low frequency sounds. The cost of an outside
barrier may be less than the cost of reducing the
d t i i i th t tisound transmission in the construction.
This type of sound barrier must completely shield the
building from the noise source. It should be placedg p
as close to the sound source as possible to obtain the
greatest sound-shadow angle. If a fence or wall is
used no louvers or openings should be permittedused, no louvers or openings should be permitted.

83. Acoustical Zoning

84. Airborne Sound
Airborne sound includes conversation, outdoor
noises, music and machine noises (machines usually
also produce impact sound) It is the major sourcealso produce impact sound). It is the major source
of intruding sound from rooms on the same floor
and from the outdoors. It is controlled by:
( i h )1. Mass (weight),
2. Isolation (decoupling),
3. Absorption3. Absorption
4. Limpness of Construction.
Th t b bi d ith i ti ht li dThese must be combined with airtight sealing and
the elimination of flanking paths (routes by which
the sound travels around a partition rather thanp
being stopped by it).

85. AbsorptionThe amount of sound energy dissipated depends on the thickness of the
material its density (which determines the amount of difficulty that thematerial, its density (which determines the amount of difficulty that the
sound encounters in traveling through), and it's resiliency (flexibility with the
ability to spring back to its original shape). Mineral wool insulation because
of its porous yet dense character, is highly effective in this application. Sound
bl k f d h h h d h h lattenuation blankets are manufactured with higher density than thermal
insulating blankets to obtain optimum attenuation. Mineral fiber sound
attenuation blankets, placed between the studs in a resilient partition with
resilient channels, retard movement of the air column and convertresilient channels, retard movement of the air column and convert
considerable sound energy into heat. However, if the diaphragms are directly
connected to rigid studs, the partition will act as a single diaphragm,
rendering the wool ineffective in dissipating sound energy.

86. Flanking Paths
Some of the most common flanking paths are
supplied bysupplied by
plumbing pipes,
air ducts and
electrical conduit rigidly connected between
the floor and ceiling.
Continuous walls between floors, columns or
any other continuous structural elements will
fl ki h f i d I fact as flanking paths for impact sound. In fact,
any rigid connection between the two
diaphragms will effectively transmit impactdiaphragms will effectively transmit impact
sound.

87. Flanking Paths

88. Architectural AcousticsArchitectural Acoustics
• Factors Affecting Architectural Acousticsg
1. Reverberation Time
• When the reverberation time is too high, the sound produced byWhen the reverberation time is too high, the sound produced by
the speaker will persist for a long period of time.
• Similarly ,when the reverberation time is low, sound dies quickly
and becomes inaudible in a short amount of timeand becomes inaudible in a short amount of time.
• In order to improve the sound, reverberation time of a hall should
be increased to an optimum value.
Remedies :‐
• Decreasing total absorption coefficient of the wall
• Placing sound reflection boards inside a hall• Placing sound reflection boards inside a hall

89. 2. Loudness
• Reverberation time of a hall is directly proportional to loudness.
• Low loudness results in existence of sound for a shorter period
hil hi h l d lt i i t f d f lwhile high loudness results in existence of sound for a longer
period.
• Therefore sound produced by the speaker should be within
audible range.
Remedies :‐
• Placing sound absorbing boards to reduce loundness• Placing sound absorbing boards to reduce loundness
• Placing sound reflecting boards to increase loudness

90. 3. Echelon Effect
• Unwanted sounds are produced when people walk on
staircase or floors or hard paved paths due to poor finishing
f h fl f l ffof the floor surface, structural effects, etc.
• The above mentioned unwanted sound are termed as
‘echelon effect’ .echelon effect .
Remedies :‐
• Finishing the floors or stairs very finely.
• Using carpet to caver floors and stairs.

91. 4. Structure‐Borne Sound
• Sound waves generated inside a hall are known as structure‐borne
sound.
Th d d d t t ti f b h &• They are produced due to apparent motion of benches &
footsteps & propagated through walls and floors.
Remedies :‐
• Using rigid structures so as to rest the vibrations.
• Introducing discontinuities in the path of sound.
C ti fl d ili ith it bl d b bi• Converting floor and ceilings with suitable sound absorbing
materials & anti‐vibration mouths.

92. 5 Echo5. Echo
• If the time interval between direct sound and reflected
sound is less than 1/15 of a second, the reflected sound is
helpful in incresing loudness.
• But if the time interval is less than that, then the sound
arrives later and will cause confusionarrives later and will cause confusion.
Remedies :‐
• To prevent unnecessary reflection of sound.To prevent unnecessary reflection of sound.
• Covering long distance walls and ceilings with suitable sound
absorbing materials.

93. 6. Focusing due to walls and ceilings
• Sound produced by speaker undergoes multiple reflections at• Sound produced by speaker undergoes multiple reflections at
ceilings and walls.
• Reflected sounds from ceilings and walls should not be focused on
particular point, rather it should be distributed throughout a hall.
• Generally a plane surface reflects sound uniformly but a curved
surface does not. So reflection of sound from a curved surface
produces a harmful effect.
Remedies :‐
R di f t f ili h ld b k t t i th h i ht f• Radius of curvature of ceilimg should be kept twice the height of
the building
• Distribution of sound waves from a concave surface should be
made uniform

94. 7 Resonance within a building7. Resonance within a building
• Sound waves get amplifies when the frequency of vibration
of air particles matches with the hall’s natural frequency of
vibration.
• Thus, it results in an unwanted sound effect in side a hall.
R diRemedies :‐
• Model‐Hall or a model auditoriun should be kept inside a
vessel which contains water.vessel which contains water.
• The water‐wave particle movememnts are studies and are
used for the construction of actual hall or auditorium.

95. ACOUSTICALACOUSTICALACOUSTICALACOUSTICAL
MATERIALSMATERIALSMATERIALSMATERIALS

96. TYPES OF MATERIALSTYPES OF MATERIALS
• SOUND ABSORBERS
• SOUND DIFFUSERS
• NOISE BARRIERS
• SOUND REFLECTORS

97. SOUND ABSORBERSSOUND ABSORBERS
• These sound absorbing acoustical panels and soundproofing
materials are used to eliminate sound reflections to improve speech
i t lli ibilit d t di d t b filt iintelligibility, reduce standing waves and prevent comb filtering.
• Typical materials are open cell polyurethane foam, cellular
melamine, fiberglass, fluffy fabrics and other porous materials. A
wide variety of materials can be applied to walls and ceilings
depending on your application and environmentdepending on your application and environment.
• These materials vary in thickness and in shape to achieve different
absorption ratings depending on the specific sound requirements.
TYPES –
Acoustical foam panels
White paintable acoustical wall panels
Fabric wrapped panels
Acoustical wall coverings
Ceiling tiles
Baffles and banners for ceiling
Fibre glass blankets and roll

98. ACOUSTICAL FOAM PANELSACOUSTICAL FOAM PANELS
• These acoustical foam sound absorbers are used in a wide variety of applications ranging
from Recording and Broadcast Studios to Commercial and Industrial Facilities. Available in
Polyurethane or in a Class 1 Fire Rated foam These products can be applied directly toPolyurethane or in a Class 1 Fire Rated foam. These products can be applied directly to
walls, hung as baffles or used as freestanding absorbers.
Design enables you to
i thi k i kl
Anechoic wedges are
ideal for controlling
l f d
STACKABLE FOAM
increase thickness quickly
by nesting layers
Standard patterns include
wedge, pyramid, max
d f l f ANECHOIC WEDGE
low frequency sound
to create a room that
is perceptually devoid
of sound.
STACKABLE FOAM
wedge for low frequency
absorption, ceiling baffles,
bermuda triangle traps for
corners, sounds cylinders
f di b b
Absorbers are lightweight
open cell foams used when a
Class 1 fire rated foam is
ANECHOIC WEDGE
CUTTING WEDGE
Installs to create seamless absorptive walls,
STANDARD POLYURETHANE FOAM PATTERNS
free standing absorbers Class 1 fire rated foam is
required. Standard patterns
include Wedge, Pyramid,
Max Wedge, Ceiling Baffles
and more These can easilyp
and enhance imaging by reducing
unwanted reflections. Available in 1'x1' or
2'x4' sheets.
and more. These can easily
mount to walls or ceilings.
FIRE RATED
FOAM

99. WHITE PAINTABLE PANELS
• It is a white acoustical wall panel with a soft textured appearance. The two foot by one foot
dimension provides installers flexibility to mount acoustical panels around existing objects.
In addition to reducing echo and reverberation, these acoustical panels are used to create
i d i d tt Th l fib i f d ith i t bl i Thiunique designs and patterns. The glass fiber core is faced with a paintable covering. This
allows you to match or complement existing wall colors by applying a light coat of flat or
matte spray paint. To customize the look even further, many local printing companies now
have the capability to produce an image directly to the face of these panels.
∞ Quick & Easy acoustical solution∞ Quick & Easy acoustical solution
∞ Soft drywall texture appearance
∞ Create unique patterns
∞ Panel size allows for flexible mounting options
∞ Paintable & Printable finish
Construction: 1 " Fiberglass 6 PCF
acoustical core + molded fiberboard
+ paintable facing. Resin hardened
d P i t bl fi i h
Sustainability
This product bears the
M tisquare edges. Paintable finish covers
face and exposed edges.
Class A rating per ASTM E 84
Panel Size: 2' x 1' (24 inches by 12
i h )
This product bears the
Green Cross label for
recycled content. The
acoustical substrate is
certified on average to
t i t l t 35%
Mounting
Installs using standard impaling clip
method. (adhesive by others) Other
mounting options shown below.
inches)
Thickness: 1-1/8"
Quantity per box: 10 panels
contain at least 35%
recycled glass, with 9%
post-consumer and 26%
pre-consumer content.
MOUNT IN CORNERS USING
CORNER CLIPS.
MOUNT ON TWO INCH STAND
OFF CLIPS

100. FABRIC WRAPPED PANELS
• Acoustical sound panels utilize 6-7 PCF glass fiber material for maximum absorption.
Available as wall panels, ceiling tiles, hanging baffles, acoustical clouds and bass traps, with
more than 50 standard colors to choose from, these materials will look as good as they
sound. The standard sizes and configurations best maximize raw materials, however, manyg y
of these products can be customized to meet specific requirements should you need material
sized to fit or other finishes or coverings.
•Ceiling clouds reduce reflected sound in areas such as
th t t t h i ll
CEILING CLOUDS
theaters, restaurants, arenas, shopping malls,
convention centers, recording and broadcast rooms, or
anywhere absorption is required.
•All surface faces and edges of the
glass fiber core are wrapped in
• Used to reduce echo and
reverberation in applications,
small and large These panels
WALL PANELS
CEILING BAFFLES
glass fiber core are wrapped in
fabric to match or accentuate
room décor . Ceiling Baffles
absorb sound on all sides and
edgessmall and large. These panels
are manufactured from a
rigid high density (6-7 PCF)
glass fiber acoustical board
and covered with an
CEILING TILES
• Ceiling Tiles are an
excellent choice for
many ceiling grid
edges.
•Sculptured sound absorbing
modular units used for walls, as
corner traps, bass traps andand covered with an
acoustically transparent
fabric.
many ceiling grid
applications requiring
high absorption.
BROADBAND ABSORBER
ceiling applications. Available in
half-rounds or quarter-rounds.

101. WALL COVERINGS
• Acoustical wall fabric is a dimensional fabric that offers excellent acoustical properties,
unmatched fade resistance, and a fire/smoke retardant class A rating. Sound channels is
resistant to moisture, mildew, rot, bacteria, and is non-allergenic. Produced with no voc’s
(volatile organic compounds) ods’s (ozone depleting substances) heavy metals or(volatile organic compounds), ods s (ozone depleting substances), heavy metals or
formaldehyde, it's the perfect acoustic fabric for offices, classrooms, conference centers or
any area where speech intelligibility is a critical factor.
Installation:
•This material is not factory trimmed. It is necessary
for the installer to cut a straight vertical edge
•Following the ribbed pattern. All edges must be butt
joined. Do not overcut edges. Cut material to
Features:
•Lightweight Acoustic Fabric
Applications:
•Conference Rooms
•Desired lengths, allowing for top and bottom
trimming. Wall carpet should be hung
•Straight up. Do not alternately reverse strips.
•Apply a premixed heavy duty adhesive directly to
•Lightweight Acoustic Fabric
•Easy to install
•Class A
•Passes Corner Burn Test
•Available in Many Colors
•Conference Rooms
•Theaters
•Hospitals
•Municipal
•Office Partitions
the wall, allowing it to dry to its maximum tackability
•Without it being overly dry. (Important!!! Adhesives
are ready mixed. Do not dilute)
•Adhesive and do not apply adhesive to the back of
•Available in Many Colors
•Durable / Abuse Resistant
•Improves Speech Intelligibility
•Office Partitions
•Schools
•Hallways
•and more...
the wall covering).
•Please be sure to follow instructions as provided by
the adhesive manufacturer.

102. CEILING TILES
• Cloudscape® Ceiling Tiles absorb noise and block sound transmission. These ceiling tiles
are designed to fit into existing 2' x 2' suspended drop tile ceiling grid systems. They may
also retrofit in a 2' x 4' ceiling grid by installing cross tees. Cloudscape® ceiling tiles may
also be ordered as a full 24" x 24" size un backed for adhesive mounting directly to walls oralso be ordered as a full 24 x 24 size, un-backed for adhesive mounting directly to walls or
ceilings.
• Ordinary ceilings take on new levels of visual excitement with these sculptured tiles. They
are available in five different patterns plus a non-patterned look to enable you to "mix and
t h" f d imatch" for your own designs.
Available Sizes:
24" x 24" (nominal)( )
Specify grid when ordering:
9/16 or 15/16

103. BAFFLES AND BANNERS
• Baffles and Banners are designed to solve acoustical problems economically in any large
cubic volume space such as arenas, gymnasiums, theaters, restaurants, and auditoriums.
Reverberation times that range from 4 to 9 seconds can be reduced to 1/2 to 2 seconds.
Speech intelligibility is greatly improved and sound intensity levels are reducedSpeech intelligibility is greatly improved and sound intensity levels are reduced
simultaneously by 3 to 12 decibels.
BAFFLES:
• Baffles are an economical way to
d d l l d l
BANNERS:
•Speech intelligibility is greatly
improved and sound intensity levelsreduce sound pressure levels and lower
reverberation times in large spaces
such as gymnasiums, theaters,
restaurants, health and fitness clubs,
t R b ti ti b l d
improved and sound intensity levels
can be simultaneously reduced by 3 to
12 decibels.
•Banners are suspended from ceilings,
bar joists or pre-engineeredetc. Reverberation times can be lowered
from a RT60 of 4 - 9 seconds down to a
RT60 of 0.5 - 2 seconds. Speech
intelligibility is greatly improved and
d i t it l l
bar joists or pre engineered
suspension systems. They are designed
to hang in a horizontal or in a
catenary fashion using edge stiffeners
or deck mounted flat with washersound intensity levels can
be simultaneously reduced by 3 to 12
decibels.
•These baffles are easily suspended from existing open truss and pre-
or deck mounted flat with washer
plates
y p g p p
engineered suspension systems. They are designed to hang in a
vertical fashion, allowing free flow of air and integrate exceptionally
well with existing sprinklers, lighting and HVAC systems.

104. SOUND DIFFUSERS
• These devices reduce the intensity of sound by scattering it over an expanded area rather• These devices reduce the intensity of sound by scattering it over an expanded area, rather
than eliminating the sound reflections as an absorber would. Traditional spatial diffusers,
such as the polycylindrical (barrel) shapes also double as low frequency traps. Temporal
diffusers, such as binary arrays and quadratics, scatter sound in a manner similar to
diffraction of light where the timing of reflections from an uneven surface of varyingdiffraction of light, where the timing of reflections from an uneven surface of varying
depths causes interference which spreads the sound.
QUADRA PYRAMID DIFFUSER
•This diffuser generates a uniform
PYRAMIDAL DIFFUSER
•This traditional industry
kh di dpolar response over a broad frequency
range using a pre-rotated pyramidal
pattern to create 16 angles of
reflection.
workhorse disperses sound
uniformly over a broad frequency
range. A quick solution to reduce
flutter echo.
DOUBLE DUTY DIFFUSER
Th P l li d i l
QUADRATIC DIFFUSER
A true quadratic•These Polycylindrical
Diffusers do twice the
work. They scatter sound
and function as a bass
t
A true quadratic
residue diffuser
designed for uniform
broadband scattering
and reducing High-Qtrap. and reducing High-Q
reflections.

105. NOISE BARRIERS
BARRIERS
These materials range from dense materials to block the transmission of airborne sound to
devices and compounds used to isolate structures from one another and reduce impact noise.
COMPOSITES
•Sound barrier materials are used
to reduce the transmission of
airborne sound. The BlockAid®
d l d h
•Composite materials are manufactured
from combinations of various materials
from open and closed celled foams to
quilted fiberglass and barrier Theseseries of products include the
standard one pound per square
foot non reinforced barrier,
transparent material when
b i i i i
quilted fiberglass and barrier. These
products are used to block and absorb
sound for machine enclosures as well as
blocking airborne sound and impact noise.
Some of these products include Compositeobservation or supervision is
required, reinforced vinyl to create
a hanging barrier partition.
Some of these products include Composite
Foams, StratiQuilt Blankets and Floor
Underlayment.
VIBRATION CONTROLVIBRATION CONTROL
•Vibration control products are used to absorb vibration energy and
prevent structural noise transmission. These include vibration damping
compounds and vibration pads, isolation hangers, and resilient clips. They
improve sound transmission loss.

106. FABRICS
• Acoustical fabrics are typically used to either absorb sound or as a cover for acoustical
panels. Some fabrics can also be used as a speaker grill cloth or as a finish on other types of
materials.
SOUND CHANNELS WALL FABRICS GUILFORD OF MAINESOUND CHANNELS WALL FABRICS
•Acoustical wall fabric is a dimensional fabric
that offers excellent acoustical properties,
unmatched fade resistance, and a fire/smoke
d l d h l
GUILFORD OF MAINE
•Guilford of Maine® Fabric is and
acoustically transparent fabric used to
cover many of our products including
retardant class A rating. Sound channels® is
resistant to moisture, mildew, rot, bacteria, and is
non-allergenic. Produced with no voc’s (volatile
organic compounds), ods’s (ozone depleting
b h l f ld h d i
y p g
acoustical wall panels, diffusers, and
corner traps. Fabric is also sold separately
as speaker grill cloth, wall covering and
for other field applications.
substances), heavy metals or formaldehyde, it's
the perfect acoustic fabric for offices, classrooms,
conference centers or any area where speech
intelligibility is a critical factor.
pp