This document discusses acoustics and noise control. It begins by defining acoustics and describing the basics of sound, including properties like amplitude, frequency, wavelength. It then explains sound propagation principles such as reflection, refraction, diffraction and absorption. Different materials and their effects on sound are described. Noise control techniques like site planning, architectural design and sound barriers are discussed. Specific examples of architectural designs that enhance sound are provided.

2.  Basics of sound
 Properties of sound
 Process of hearing
 Behavior of sound
 Acoustics for functional areas
 Noise control methods and techniques

3.  “a science that deals with the production, control,
transmission, reception, and effects of sound.”
 acoustics is the science of sound and of its effects on
people.
 Sound: is the sensation caused in the ear by the
vibration of the surrounding air or other medium.
 Noise: unwanted sound.

4.  Sound is reflected, transmitted, or absorbed by the materials it
encounters.
 Soft surfaces, such as textiles, and batt insulation, tend to absorb
sound waves, preventing them from further motion.
 Hard surfaces, such as ceramic tile, gypsum board, or wood, tend
to reflect sound waves, causing ‘echo’. Reverberation is the term
used to describe sound waves that are reflected off of surfaces.
 Dense, massive, materials, such as concrete or brick, tend to
transmit sound waves through the material.

5.  High frequency sound waves (think of a high whistle) are not
capable of being transmitted through massive, heavy, material.
 Low frequency sound waves (bass) are transmitted through
massive materials.

8.  Fatigue
 Irritation
 Loss of efficiency
 Permanent damage
Source:
 Road traffic noise
 Air craft noise
 Noise from railroads
 Construction noise
 Noise in industry
 Noise in building
 Noise from consumer products

9.  Reflection
 Deflection
 Diffraction
 Absorption

10. Reflection
 Reflection occurs when a wave strikes an
object and bounces off of it.
 All types of waves⎯including sound, water,
and light waves⎯can be reflected
 When a wave reaches the boundary between
one medium another medium, a portion of the
wave undergoes reflection and a portion of the
wave undergoes transmission across the
boundary., the amount of reflection is
dependent upon the dissimilarity of the two
media. For this reason, acoustically minded
builders of auditoriums and concert halls avoid
the use of hard, smooth materials in the
construction of their inside halls.

11. Texcture of wall
Smooth
Smooth walls have a tendency to direct sound waves in a
specific direction. Subsequently the use of smooth walls in an
auditorium will cause spectators to receive a large amount of
sound from one location along the wall; there would be only one
possible path by which sound waves could travel from the
speakers to the listener. The auditorium would not seem to be as
lively and full of sound.
Rough
Rough walls tend to diffuse sound, reflecting it in a variety of
directions. This allows a spectator to perceive sounds from every
part of the room, making it seem lively and full. For this reason,
auditorium designers prefer construction materials that are rough
rather than smooth.

12. Shape of material
Flat or plane surface
It reflect sound waves in such a way that the angle at which
the wave approaches the surface equals the angle at which
the wave leaves the surface.
curved surface
Curved surfaces with a parabolic shape have the habit of
focusing sound waves to a point. Sound waves reflecting off
of parabolic surfaces concentrate all their energy to a single
point in space; at that point, the sound is amplified. Perhaps
you have seen a museum exhibit that utilizes a parabolic-
shaped disk to collect a large amount of sound and focus it at
a focal point. If you place your ear at the focal point, you can
hear even the faintest whisper of a friend standing across the
room.

13. Shape of material
A CONVEX SURFACE A CORNER REFLECTOR

14.  Echo
 Sometimes when the sound waves hit another object, they reflect off it and
come back to you.
 Your ears hear the sound again, a few seconds after you first heard your
footstep.
 Sonar
 Sonar (originally an acronym for SOund Navigation And Ranging) is a
technique that uses sound propagation (usually underwater, as in submarine
navigation) to navigate, communicate with or detect objects on or under the
surface of the water, such as other vessels.

15. Law of Reflection
 The angle formed by the incident beam and the
normal is the angle of incidence.
 The angle formed by the reflected beam and the
normal is the angle of reflection.
 According to the law of reflection, the
angle of incidence is equal to the angle
of refection. All reflected waves obey this law.

17.  Refraction
 Refraction is the bending of a wave caused by a change in its
speed as it moves from one medium to another.

18.  Refraction
 When a wave passes from one medium to another⎯such as when a light
wave passes from air to water⎯it changes speed.
 If the wave is traveling at an angle when it passes from one medium to
another, it changes direction, or bends, as it changes speed.

19.  Refraction
 Sound wave will refract if there is a difference in air temperature.
 The different densities cause the waves to bend.
.

20.  Deflection

21.  Diffraction
 Diffraction occurs when an object causes a wave to change direction and
bend around it.
 Diffraction and refraction both cause waves to bend. The difference is
that refraction occurs when waves pass through an object, while
diffraction occurs when waves pass around an object.

22. Absorption
 Absorption convert sound energy into heat energy and is used to reduce
sound levels within rooms.
 Acoustic absorption is of particular interest in soundproofing.
Soundproofing aims to absorb as much sound energy (often in particular
frequencies) as possible converting it into heat or transmitting it away
from a certain location.

23. An important acoustical
measurement called Reverberation
Time (RT or RT(60)) is used to
determine how quickly sound decays
in a room. Reverberation time
depends on the physical volume and
surface materials of a room. Large
spaces, such as cathedrals and
gymnasiums, usually have longer
reverberation times and sound
“lively” or sometimes “boomy.”
Small rooms, such as bedrooms and
recording studios, are usually less
reverberant and sound “dry” or
“dead.”

24. Definitions
 Wavelength
 A sound wave is a variation in air pressure, while in light and
other electromagnetic radiation the strength of the electric and
the magnetic field vary

25.  Amplitude
 The amplitude of a periodic variable is a measure of its change over a
single period.

26.  Frequency
 Frequency is the number of occurrences of a repeating event per
unit time.

27.  The differences between the sounds—how high or low and how loud or soft they
are—depend on the properties of the sound waves
 The speed of sound depends only on the medium through which the sound is
traveling
Speed of Sound in Different Media
at 20 degrees Celsius
Medium Speed
m/s)
Air 343
Helium 1,005
Water 1,482
Sea Water 1,522
Wood (oak) 3,850
Glass 4,540
Steel 5,200
In general, the cooler the medium, the slower the speed of
sound
This happens because particles in cool materials move
slower than particles in warmer materials
When the particles move slower, they transmit energy
more slowly Therefore, sound travels more slowly in cold
air than in hot air

28. The pitch of a sound is determined by the frequency of the sound wave
The higher the frequency the higher the pitch
The average human ear can detect sounds that have frequencies between 20Hz and
20,000Hz.
Young children can often hear sounds with frequencies above this range, while many
elderly people have difficulty hearing sounds higher than 8,000Hz
Range of hearing in Hertz

29. Doppler effect
As an object moves away from you, this causes the waves to be farther apart
and to have a lower frequency
As an object moves toward you, this causes the waves to be closer together
and to have a higher frequency

30.  The softest sound a person can hear with normal hearing
 10 normal breathing
 20 whispering at 5 feet
 30 soft whisper
 50 rainfall
 60 normal conversation
 110 shouting in ear
 120 thunder

31.  The human ear's response to sound level is roughly logarithmic (based on
powers of 10), and the dB scale reflects that fact.

 An increase of 3dB doubles the sound intensity but a 10dB increase is
required before a sound is perceived to be twice as loud.
 Therefore a small increase in decibels represents a large increase in
intensity.
 For example - 10dB is 10 times more intense than 1dB, while 20dB is 100
times more intense than 1dB.
 The sound intensity multiplies by 10 with every 10dB increase.

32.  130dB - Jack Hammer (at 5ft)
 120dB - Rock Concert / Pain threshold
 110dB - Riveter or a Heavy Truck at 50ft
 90dB - Heavy Traffic (at 5ft)
 70dB - Department Store or a Noisy Office
 50dB - Light Traffic
 30dB - Quiet Auditorium
 20dB - Faint Whisper (at 5ft)
 10dB - Soundproof room / anechoic chamber

33.  sound travels at 1130 feet per second at normal room temperature.
 light travels at 299,792,458 meters per second, which is roughly
974,325,489 feet per second (974 million feet per second!!)

34.  Reverberation time refers to the amount of time required for the sound
field in a space to decay 60dB, or to one millionth of the original power.
 In simple terms this refers to the amount of time it takes for sound energy
to bounce around a room before being absorbed by the materials and air
 Reverberation time is important because it can affect how well you
understand speech, and it can change the way music sounds.
 The effect on speech intelligibility is noticeable in a gymnasium or arena,
where you often can't understand someone who is only 10 or 15 feet
away from you

35.  Reflections are an important part of acoustical design for music
performance venues.
 For effective musical acoustics, the reflections have to arrive within
the correct time window, and from the correct direction.
 The reflections help to boost the level of acoustic instruments and
human voices in the audience area.
 They also influence timbre and help define the apparent size or
perspective of the instruments.
 The critical time interval we're talking about is a very brief 0.3
seconds

38. Typical sound Absorber
 Acoustic Panels
 Membrane
 Drapes
 Foams
 Carpets

48. A
D
CB
E

51. A) Earth Berms
An earth berm, a long mound of earth running parallel to the highway, is one of the most frequently used barriers. Figure 4.17 shows a cross-section of a berm.
Earth Berms
An earth berm, a long mound of earth running parallel to the
highway, is one of the most frequently used barriers. Figure
shows a cross-section of a berm.

52. Wall barriers
It may reflect sound from one side of the highway to the other.

56. Walls
Walls provide building occupants with the most protection from exterior noise. Different wall materials and designs
vary greatly in their sound insulating properties. Figure provides a visual summary of some ways in which the
acoustical properties can be improved:
Factors which influence sound attenuation of walls

57. Factors which influence sound attenuation of walls
Increase the mass and stiffness of the wall.
In general, the denser the wall material, the more it will reduce noise. Thus, concrete walls
are better insulators than wood walls of equal thickness. Increasing the thickness of a wall is
another way to increase mass and improve sound insulation. Doubling the thickness of a
partition can result in as much as a 6 dB reduction in sound

60. Rainham Mark Grammar
School
Custom designed treatment to
improve the acoustics of a small
recital hall in a new music block.
Fabric covered melamine foam
panels, symmetrically arranged to
provide the desired level of sound
absorption

61. Architecture can also amplify the
natural noises around us. These
wooden ‘Ruup’ megaphones in
Estonia’s Võru County were constructed
in September 2015 to harness the
sounds of the forest. Designed by
students and planted amongst the
trees, the ‘bandstands’ vary in size and
form but, at 3m diameter, they are the
perfect size to climb into.

62. A quarry might seem an unlikely destination
for an opera but people across the world are
wising up to the potential of these vast,
cavernous spaces. The Hungarian Fertőrákos
Cave Theatre recently reopened following
renovation work, while Portugal’s Estremoz
marble quarries host performances on an ad
hoc basis. Sound resonates within their
solid walls in an interplay with light and
shadow.
Fertőrákos Cave Theatre, Hungary

63. Further evidence of a nation using architecture to enhance its traditional music takes us to
Iran – amid some 17th-century mud bricks, to be precise. The Āli Qapu Palace Music Hall’s
magnificent vaulted ceilings create an umbrella of niches overhead, which mean a low
reverberation time for sound – ideal for intimate music, and specifically, Iranian ballads.

64. On the UK coast near
Dungeness, ‘sound mirrors’ are
part of the landscape. These
concrete forms, ranging from 20 to
200 feet wide, were constructed in
the 1920s as early warning devices
for approaching enemy planes.
When aircraft and radar
technology advanced, they quickly
became redundant but the sonic
qualities of these enduring
landmarks remain.

65. The whispering gallery
phenomenon – where a
noise you make on one side
of a space can be clearly
heard on another – is often
unintentional. Yet, at
London’s St Paul’s Cathedral,
it draws tourists in droves.
Mutter a little something
into the gallery wall and it
can be heard on the other
side of the 33m diameter
dome. Just be careful what
you say…

66. On 12th July 2013 St Paul's Cathedral was transformed into a
magical Live Music Sculpture by the composer Samuel
Bordoli. 27 musicians were arranged throughout the cathedral
in 6 separate locations including the Whispering Gallery and
multi-level triforium galleries. The sound appeared to emerge
from the cathedral walls themselves as is floated through the
space, playing with the acoustics and the architectural form of
the building. www.livemusicsculpture.com
Samuel Bordoli Live Music Sculpture 3: St
Paul's Cathedral

67. Physical
Technique
Potential
Effectiveness
Situations
Where Most
Effective
Cost Relevant
Administr
ative
Technique
Comments
Acoustical
Site Planning
Good-
excellent:
depends on
size of lot and
natural
terrain.
Before
building
construction,
before
subdivision
development
Low. only
costs are
fees of
acoustical
consultant
and site
planner.
Building
code*
Health
code
Fairly
inexpensive but
requires space
which may be
unavailable.
Has limited
sound
reduction.
Positive
aesthetic
impacts.
Acoustical
Architectural
Design
Fair Before
building
construction.
Low: only
cost is that
of acoustical
consultant
Building
code*
Health
code
Low cost but
limited
effectiveness.

68. hysical
Technique
Potential
Effectiveness
Situations
Where Most
Effective
Cost Relevant
Administrative
Technique
Comments
Acoustical
construction.
Excellent for
interior, poor
for exterior.
During building
construction
best. Most
costly after
construction.
Varies with
amount of
noise reduction
desired but
generally high
especially after
construction.
Building code*
Health code
Most effective
noise reduction
for interiors
Barriers Fair-excellent,
depends on
height and
mass
Varies with
type of barrier
Moderate-high:
varies with type
of barrier, see
below.
Zoning,
subdivision
rules, health
code
High noise
reduction and
potentially low
cost. Achieves
exterior noise
reduction.Can
have adverse
aesthetic
impacts.

69. hysical
Technique
Potential
Effectiveness
SituationsWhere
Most Effective
Cost Relevant
Administrative
Technique
Comments
Earth Berms Good-excellent Best during road
construction when
earth is available.
Costly after road
construction.
Impractical in
densely populated
areas where land
is scarce.
Moderate-
high: depends
on availability
of earth.
Good noise
reduction
properties and
aesthetic
appeal, but
requires space
and requires
maintenance.
Walls and
Fences
Poor-excellent,
depends on
height and
mass
Any time Low-high:
depends on
height and
thickness.
Requires little
space and no
maintenance,
but may be
aesthetically
unappealing
and can reflect
noise to other
side of road.

70. hysical
Technique
Potential
Effectiveness
Situations
Where Most
Effective
Cost Relevant
Administrative
Technique
Comments
Plantings Poor After road
construction.
After building
construction.
Moderate high:
depends on
size of buffer
strip.
Poor noise
reduction but
often
necessary for
aesthetic
appeal. Best
used in
combination
with other
techniques.
Combinations Good-
excellent.
Depends on
particular
combination.
Moderate-
high: depends
on type of
barrier used
Potentially
high noise
reduction and
aesthetic
appeal.