acoustic control and their defects

1. 1

2. BUILDING SERVICES
Submitted by
Name – Neeru and Aprajeeta
B.Arch- 5th
sem/ 3rd
year
From – R.T.I.A And D 2

3. Contents
Introduction About the Acoustics
Characterstics
Acoustic defects
Acoustic solution
Material
Case study of a hotel
3

4. ACOUSTIC
related to the sound or the sense of hearing
Introduction :- Acoustic is the science of sound as
applied to buildings it deals with the origin
propagation and auditory sensation of the sound.
Knowledge of the science is used for the design and
construction of theaters, cinemas, concert halls,
auditorium etc.
Proper acoustical conditions also include the sound
absorption or dissipation of the exterior noise.
4

5. Acoustics means to work on these three parameters and improve
sound experience.
5

6. Transmission loss (TM) of sound
•When sound is transmitted from source or origin to the
adjoining room/ area, reduction in sound intensity takes place.
•This is known as transmission loss (TM)
•Measured in decibels (dB)
60 decibels 40 decibels
TM=60-40=20 DECIBELS.
6

7. Flanking path: Path between adjacent spaces other than through common partition through which
sound or vibration is transferred 7

8. Sound and vibrations
 Sound is a vibration in an elastic medium such as air, water, most building
materials, and the earth.
(Noise can be defined as unwanted sound, that is, annoying sound made by
others or very loud sound which may cause hearing loss).
Frequency of sound
Frequency is the rate of repetition of a periodic event.
The unit of frequency is the hertz (Hz)
Wavelength
As sound passes through air, the to-and-fromotion of the particles alternately pushes
together and draws apart adjacent air particles, forming regions of rarefaction and
compression.
Wavelength is the distance a sound wave travels during one cycle of vibration.
Example-Sound waves in air also are analogous to the ripples (or waves) caused
by a stone dropped into still water. The concentric ripples vividly show
patterns of molecules transferring energy to adjacent molecules
along the surface of the water. In air, however, sound spreads in
all directions.
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9. Velocity of sound
Sound travels at a velocity that depends primarily on the elasticity
and density of the medium.
In air, at normal temperature and atmospheric pressure, the velocity of sound is
approximately 1,130 feet per second (ft/s), or almost 800 mi./h. This is extremely slow
when compared to the velocity of light, which is about 186,000 mi./s, but much faster
than even hurricane winds.
Frequency ranges of audible sounds
Hearing ranges for both young and older persons (> 20 years old)
A healthy young person is capable of hearing sound energy from
about 20 to 20,000 Hz. Hearing sensitivity, especially the upper
frequency limit, diminishes with increasing age Even without
adverse effects from diseases and noise—a condition
called “presbycusis.”
Human speech contains energy from about 125 to 8000 Hz. Women’s
vocal cords are generally thinner and shorter than men’s, so the
wavelengths
9

10. 10

11. CHARACTERSTICS
Sound consist of a series of alternate compression and rarefaction that
are set by a vibrating body.
The sound in the form of wave travel in the direction through any
medium.
The average velocity of sound in air can be taken as 343 m/s.
Flow of sound energy per unit time through unit area is termed as
intensity of loudness of sound.
Frequency or pitch of audible sound is defined as the no of cycles or
vibrations per second that strikes the ears.
Good acoustical buildings promote comfortable living, efficiency of
work, auditory or public buildings etc.
Hence, modern design of buildings and construction should give
importance to the improvisional of acoustical conditions and sound
insulation so as to exclude of diminish the noise.
11

12. 12

13. ACOUSTIC DEFFECT
When the average sound intensity rises in to a suitable level in every
part of the room or auditorium with no echoes or disturbances or
distortions. This is called acoustic of building. To achieve this, one has
to minimize the defects. Following are the main defects of sound-
Formation of Echoes
Reverberation of Sound
Insufficient loudness
Sound focl
Dead spots
Outside or External disturbance
13

14. FORMATION OF ECHOES-
Echoes mainly produced due to the reflection of sound wave(mainly
from the surface of walls, roofs, ceilings etc.)
Echo is founded when the reflected sound reaches the ear at the same
time when a direct sound reaches. Echo causes disturbance and
unpleasant hearing.
When Not all sound is absorbed, Some of it is reflected, That means sound bounces off the
solid matter example- a tennis ball bounces off a wall. Sound reflected back to its source is
an echo. 14

15. This defect can be removed by selecting proper shape of the hall .
And by providing rough and porous interior surfaces to disperse the
energy of echoes.
And by providing rough and porous interior surfaces to disperse the
energy of echoes.
This defect can be removed by selecting proper shape of the hall .
•Echoes are the reflection of sound from relatively flat object that is far enough away that
you can discern the time difference. Echoes are used to measure distance, velocity, and
the shape of objects. Echoes off gratings result in an unusual pinging sound.
•repetition of sound
•The sensation of sound persists for 1/15th
of a second after the source has ceased. Thus
an echo must reach after 1/10th
second of the direct sound .
15

16. Reverberation
Is the time interval with in which , the intensity of sound produced
or
reverberation is the multiple reflection in an enclosed space .
The sound persists even when the source of sound has ceased or
stopped.
This phenomena of sound is called reverberation.
16

17. 1..Depends on the size of room as if room is small reflections will taken
place quickly as waves have to travel less distance, so time will be less.
2.Reverberant sound is the reflected sound , as a result of improper
absorption.
3.Reverberation may results in confusion with the sound created next.
The time during which the sound persists is called the reverberation
time of sound in the hall.
reverberation time ‘t’ is given by formula :-
t= 0.16V /A where V=volume of room in cubic meters
A= total absorbing power of all the
surfaces of room/ hall.
Reverberation time: Amount of time at a specific frequency that a sound in an enclosed space takes
to decrease 60 decibels in level after the source sound has stopped.
17

18. Reverberation time & quality of sound
Reverberation time should remain within limits as
per Indian Standard Code: 2526-1963.
Sr.
No.
RECOMMENDED TIME IN
SECONDS
ACOUSTICS
1 0.50 to 1.50 Excellent
2 1.50 to 2.00 Good
3 2.00 to 3.00 Fairly good
4 3.00 to 5.00 Bad
5 Above 5.0 seconds Very bad
18

19. INSUFFICIENT LOUDNESS :-
In case of theater or large auditoriums the speakers voice or music
from the stage should be easily audible in all parts of the hall at the
uniform of intensity of loudness. To achieve this,
the sound waves should be properly reflected and uniformally spread
all over the interior part of the auditorium.
But due to the lake of sound reflecting flat surfaces near the sound
source or stage and excessive absorption of sound in the hall resulting
the defect of insufficient loudness.
This defect can be minimized by providing hard surface near the stage
absorbent material should be provided as per the requirements.
Also the location of loudspeakers should be adjusted.
So that there is no dead spots and sound focl.
19

20. Sound focl
Reflecting concave surfaces cause concentration of the reflected
sound wave at certain spot, creating a sound of large intensity. These
spots are called sound focl.
This defect can be remove by :-
1. Geometrical designed shapes of the interior faces, including ceilings.
2. Providing highly absorption materials on focusing areas.
20

21. Dead spots
1. This defect is an outcome of the formation of
sound focl.
2. Because of high concentration of the of
reflected sound at spot focl, there is
deficiency of reflected sound at some other
points.
These points are known as dead spots, where
sound intensity is so low that is insufficient
for hearing.
This defect can be remove by
Installation of suitable diffuser and
reflectors so that there is even distribution
of the sound in the hall.
21

22. Outside or External disturbance
External noise from vehicles, traffic engines, factories, cooling plants
etc. may enter the hall either through the openings such as doors
windows, ventilators etc. or through the walls and other structural
elemens having improper sound insulation .
Sources of outdoor noises
Road traffic.
Railways.
Climatic conditions.
Aero planes.
Moving machines.
Machines in nearby factories or buildings etc.
Sources of in door noises
Indoor noises are those which are caused
either in the same room or adjacent rooms.
And these are due to:-
Conversation of peoples.
Moving of peoples .
Moving of furniture.
Crying of babies.
Playing of radios/ other musical
instruments.
Operations of water closets and
cisterns.
Noise of type writer
Banging of doors etc.
This defect may be removed by-
By using sound insulation material on the walls with respect to the surroundings. 22

23. Absorptive surfaces are primarily used for the following
applications:
- Reverberation Control: reduction of reverberant sound energy to improve speech
intelligibility and source localization.
- Sound Level Control: reduction of sound or noise buildup in a room to maintain
appropriate listening levels and improve sound
isolation to nearby spaces.
- Echo and Reflection Control: elimination of perceived single echoes, multiple flutter
echoes, or unwanted sound reflections from room surfaces.
- Diffusion Enhancement: mixing of sound in a room by alternating sound absorptive and
sound reflective materials.
Acoustics solutions
23

24. Sr. no. Name of
acoustics
material
Characteristic Image
1. Carpet Carpet absorbs airborne noise as
efficiently as many specialized
acoustical materials.
2. Quiet
barrier
HD
Reducing airborne noise transmission
through walls, ceilings and floors.
3. Quiet
barrier
MD
To reduce noise transmission
between two spaces.
4. Quiet Batt A premium high-performance
acoustical/thermal insulation
manufactured from 80% recycled
cotton fibers.
5. Tough
core
Ceiling
Tiles
Especially well-suited to minimize
sound transmission between adjacent
spaces sharing a common attic
space.
6. Isotrax Blocks and isolates sound, reduces
noise from traveling through building 24

25. Types of sound insulating materials
Non porous rigid.
Porous rigid materials.
Non rigid porous flexible materials.
25

26. 1.Non porous
rigid
• Brick masonry
• plastered on
both sides
• Stone
masonry
structures
• Concrete/RCC
structures
2.Porous rigid
materials.
•Light weight
concrete
•Cellular concrete
•Gypsum board
partitions
3. Non rigid porous
flexible materials
•Perforated boards
•Compressed fiber
boards
•Pulp boards
•Mineral wool boards
•Acoustic tiles /sheets
•Glass wool
Types of sound insulating materials
26

27. Absorptive surfaces be any of three basic types of materials:
- Porous materials include fibrous materials, foam, carpet, acoustic
ceiling tile, and draperies that convert sound energy into heat by
friction. Example: fabric-covered 1 in. (2.5 cm) thick fiberglass
insulation panels mounted on a wall or ceiling.
- Vibrating panels thin sound-reflective materials rigidly or resiliently
mounted over an airspace that dissipate sound energy by
converting it first to vibrational energy.
Example: a 1/4 in. (6 mm) plywood sheet over an airspace (with or without fibrous materials
in the airspace).
- Volume resonators - materials containing openings leading to a hollow cavity in which
sound energy is dissipated. Example: slotted concrete blocks (with or without fibrous
materials in the cores).
27

28. Sound insulating techniques/Solutions
There are some construction techniques also which are adopted
for sound insulation.
Double wall construction.
Cavity wall construction.
False ceiling.
Hollow block construction.
Sound insulation in floors.
Double pane windows.
Baffle blocks, honey combs etc.
28

29. Double wall construction .
BOARDS WOODEN STUDS
SOUND ABSORBING BLANKET
BOARDS
WOODEN STUDS
29

30. Cavity wall construction.
EXTERNAL WALL 13MM
PLASTERED
5CM CAVITY
BRICK WALL 10CM
CELOTEX OR OTHER INSULATING
BOARD
METAL FLY
30

31. False ceiling.
REINFORCED CONCRETE ROOF
SUSPENDERS
FALSE CEILING
31

32. Hollow block construction.
COMPRESSED CONCRETE HOLLOW BLOCKS
HOLLOW
32

33. Sound insulation in floors
33

34. Sr. no. material name Application co-efficients
1. Brick wall painted 0.023
2. 6mm thick carpet or felt on solid concrete floor 0.65
3. Curtains light, 3kg/sq. m 0.30
4. Curtains medium 0.40
5. Curtains heavy 5.5 kg/sq.m. 0.82
6. Chairs metals or wooden 0.019
7. Chair with leather cushion 0.07
8. Compressed paper board 0.11
9. Floor concrete 0.02
10. Floor timber 0.03
11. Fibre board 12mm thk 0.3
12. Foamed concrete 0.20
13. Glass wool or slag wool 50mm thk fixed on
battens secured to solid wall
0.95
14. Plaster, gypsm or line smooth finish or brick 0.04 34

35. Sr. no. Material name Application co-efficient
15. Plaster, gypsum or lime on lath over solid backing 0.04
16. Perforated fibre board tiles 18mm thk bedded
solidly
0.8
17. Plywood panelling fixed on battens keeping about
2mm thk, air gap between the panelling and the
solid wall
0.1
18. Brick wall unpainted 0.023
19. Linoleum or asphalt laid on concrete floor 0.03
35

36. Case
study
of a
hotel
36

37. Reception of the K. Hotel
Wooden use on the
wall and on the
columns as an
decoration purpose
which is control the
acoustics in the
reception area.
Co-efficient of
wooden .25-.5
1. only one side
on the wall
method is to be
used.
Section of the
wooden
panelling on
wall
37

38. Sound insulation in column and in ceillng
38

39. Doors of the hotel
All doors in k hotel are wooden either washrooms or service areas 39

40. Wooden as an decorative material but the
purpose is same more absorption of sound
Wooden panel are
also used on the walls
for the sound
absorption or as an
decoration purpose
And
On the columns also
wooden used. Air
spaces are to be left
in the panelling
40

41. This was also
wooden as an
decorative
material. It was
an hollow an
inner part.
41

42. Furniture in the hotel
42

43. Sound insulation in ceiling and the
flooring
43

44. Some other material or
thing used for the sound
insulation, co- efficient of
medium curtains 0.40
44

45. Type of glazing with
the wooden frames,
co-efficient of glass
0.04
45