1. Acoustics and sound insulation
PREPARED BY MANISH KUMAR
LECTURER ARCHITECTURE
AT GOVT. POLY. COLLEGE FOR GIRLS PATIALA
PRESENTATION BY MANISH KUMAR LEC. ARCHITECTURE AT PATIALA

2. GENERAL INTRODUCTION
Sound is generated in the air when a surface is vibrated.
The vibrating surface sets up waves of compression and rarefaction.
To understand it let us take example of tuning fork
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3. GENERAL INTRODUCTION
I have drawn three pictures of a tuning fork to help you visualize how air molecules might look around a tuning fork.
When the tuning fork is at rest, the fork is surrounded by molecules in the air.
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4. GENERAL INTRODUCTION
As a tuning fork's prongs move apart because of a vibration.
The molecules ahead of it are crowded together.
They look like they are being pushed together. They bump each other.
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5. GENERAL INTRODUCTION
As the tuning fork's prongs come back together, it leaves a region that has fewer molecules than usual.
The region of a sound wave in which the molecules are crowded together is a compression.
The region of a sound wave in which particles are spread apart is a rarefaction.
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6. GENERAL INTRODUCTION
As a tuning fork vibrates, it causes molecules in the air to move.
The molecules bump into other molecules nearby, causing them to move.
This process continues from molecule to molecule.
The result is a series of compressions and rarefactions that make up sound waves.
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7. GENERAL INTRODUCTION
And these compression and rarefactions sets the ear drum vibrating.
The movements of ear drum are translated by the brain into sound sensation.
So, we really don't hear with our ears - we hear with our brains!
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8. GENERAL INTRODUCTION
Shape (dish type) of the outer ear is helpful in receiving sound waves.
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9. GENERAL INTRODUCTION Here's How It Works
Sound vibrations, or sound waves, are collected by the OUTER EAR.
And travel into the ear canal, where they bump up against the ear drum.
The EAR DRUM vibrates in sympathy with these sound waves.
As it vibrates, it moves a series of tiny bones in the MIDDLE EAR
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10. GENERAL INTRODUCTION
Which carry the vibrations to a fluid-filled tube called the cochlea in the INNER EAR
The fluid inside the cochlea vibrates a series of tiny hairs called cilia, which are attached to auditory nerves.
The movement of these cilia stimulates the nerves.
And they send signals to the brain, which, in turn, processes these signals into the sounds we hear.
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11. GENERAL INTRODUCTION
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12. Characteristics of sound
There are three characteristics of sound.
Intensity and loudness and it is measured in decibel
Frequency and pitch of sound it is measured in “Hertz" (Hz) or "cycles per second”.
Quality or timbre of sound.
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13. Intensity and loudness of sound
Intensity of the sound is defined as the amount or flow of wave energy crossing per unit time through a unit area taken perpendicular to the direction of propagation.
Intensity of sound is purely a physical quantity which can be accurately measured and is independent of the ear of the listener.
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14. Intensity and loudness of sound
Loudness of a sound corresponds to the degree of sensation depending upon the intensity of sound and sensitivity of ear drums.
It may also happen that the same listener might give different judgments about the loudness of sound of the same intensity but of different frequencies as the response of the ear is found to vary with the frequency of vibration.
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15. Frequency and pitch of sound
Frequency or pitch is defined as the number of cycle which a sounding body makes in each unit of time.
It is measure of the quality of sound.
The sensation of pitch depends upon the frequency with which the vibrations succeed one another at the ear.
Greater the frequency the higher the pitch.
And the lesser the frequency the lower the pitch.
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16. Frequency and pitch of sound
The audio range falls between 20 Hz and 20,000 Hz. This range is important because its frequencies can be detected by the human ear.
A frequency is expressed in terms of Hz(Hertz)
and it determines pitch of sound source. They can be categorized as:
Low tones –sound of urban road traffic.
Mild tones –sound of piano notes.
High tones –sound of single tea kettle.
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17. Quality or timbre of sound.
The quality of sound is that characteristics which enables us to distinguish between two notes of the same pitch and loudness played on two different instruments or produced by two different voices.
It is to be noted that it is that tonal quality which enables us to recognize a large number of different sounds.
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18. The behavior of sound propagation
It is affected by many things:
The speed of sound within the medium depends upon temperature of the medium ,which in turns effect the density and pressure of the medium..
The propagation is also affected by the motion of the medium itself.
For example, sound moving through wind is further transported towards the direction of wind.
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19. The behavior of sound propagation
The viscosity of the medium also affects the motion of sound waves.
It determines the rate at which sound is attenuated.
For many media, such as air or water, attenuation due to viscosity is negligible.
Sound cannot travel through a vacume.
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20. The behavior of sound propagation
It travels much faster in solids and liquids then in air.
The velocity of sound in atmospheric air at 20 degree centigrade is 343 meter per second.
The velocity of sound in pure water is 1450 meter per second.
The velocity of sound in bricks is 4300 meter per second.
The velocity of sound in concrete is 4000 meter per second.
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21. The behavior of sound in enclosures
When the sound waves strike the surface of room three things happen
Some of the sound is reflected back in the room.
Some of the sound energy is absorbed by the surfaces and listeners of the room/hall .
And some of the sound is transmitted out of the room through vibrations of floors, walls and ceilings.
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22. The behavior of sound in enclosures
The amount of sound reflected and absorbed depends upon the different surfaces of room.
And the sound transmitted outside the room will depend upon .
The sound insulation properties of walls , floors and ceiling etc. .
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23. Reflection of sound waves.
Reflection of sound waves is exactly the same as that of light waves.
That is angle of incidence is equal to the angle of reflection. *c
REFLECTED WAVE
INCIDENT WAVE *c *c
REFLECTING SURFACE.
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24. Reflection of sound waves.
The reflected wave front from a flat surface are also spherical and their centre of curvature is the image of source of sound.
FLAT REFLECTOR
WAVE FRONT
SOUND SOURCE
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25. Reflection of sound waves.
Sound waves reflected at a convex surface are magnified and are considered bigger.
They are attenuated and therefore weaker.
So convex surface may be used with advantage to spread the sound waves throughout the room.
WAVE FRONT
CONVEX REFLECTOR
SOUND SOURCE
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26. Reflection of sound waves.
The sound waves reflected at a concave surface are considered smaller.
The waves are most condensed and therefore amplified.
The concave surface may be provided for concentration of reflected waves at certain points.
CONCAVE REFLECTOR
WAVE FRONT
SOUND SOURCE
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27. Acoustics general introduction
The scientific study of the phenomenon of sound is known as Acoustics.
Acoustics as applied to buildings is the science of sound which assures the optimum conditions for
Producing sound/speech/music
Listening of sound/speech/music
Recording /editing of sound etc.
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28. Acoustical Interaction
Acoustics means to work on these three parameters and improve sound experience.
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29. Acoustical Interaction
Sound is attenuated by absorption
Historically, the primary focus of acoustics was the use of absorbing surfaces to control the reverberation times and loudness of spaces.
Redirected by reflection
Uniformly scattered by diffusion
Good architectural acoustic design requires an appropriate combination of absorptive, reflective and diffusive surfaces
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30. Acoustics general introduction
For better acoustical results the construction and application of sound absorbents and sound reflective materials should be carefully selected and placed.
This will help in providing better quality of audio video sensations to viewers/ listeners.
Proper acoustical planning can reduce or completely eliminate defects related to sound ,which are called acoustical defects.
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31. Acoustical defects List of acoustical defects Reverberation.
Formations of echoes.
Sound foci.
Dead spots.
Insufficient loudness.
Exterior noises.
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32. Acoustical defects (Reverberation)
Reverberation is the persistence of sound in the enclosed space , after the source of sound has stopped.
Reverberant sound is the reflected sound , as a result of improper absorption.
Reverberation may results in confusion with the sound created next.
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33. Acoustical defects (Reverberation)
However some reverberation is essential for improving quality sound.
The time during which the sound persists is called the reverberation time of sound in the hall.
As per Prof. W .C. Sabins 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.
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34. Acoustical defects (Reverberation)
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35. Acoustical defects (Reverberation)
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36. Reverberation time & quality of sound
Reverberation time should remain within limits as per Indian Standard Code:
Sr. No.
RECOMMENDED TIME IN SECONDS
ACOUSTICS 1 to
Excellent 2 to
Good 3 to
Fairly good 4 to
Bad 5
Above seconds
Very bad
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37. Formation of echoes. Echo's
Not all sound that hits matter is absorbed. Some of it is reflected. That means sound bounces off the solid matter the way a tennis ball bounces off a wall. Sound reflected back to its source is an echo.
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38. Formation of echoes.
An echo is produced when the reflected sound wave reaches the ear just when the original sound from the same source has been already heard.
Thus there is repetition of sound.
The sensation of sound persists for 1/10th of a second after the source has ceased.
Thus an echo must reach after 1/10th second of the direct sound
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39. Formation of echoes.
Multiple echoes may be heard when a sound is reflected from a number of reflecting surfaces placed suitably.
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.
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40. Sound foci
Some times shape of the hall makes sound waves to concentrate in some particular areas of hall creating a sound of large quality.
These spots are called sound foci.
This defect can be removed by
Geometrical design shapes of the interior faces.
Providing highly absorbent materials on critical areas (curved spaces).
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41. Dead spots. This defect is the out come of formation of sound foci.
Because of high concentration of reflected sound at sound foci , there is deficiency of related sound at some other points.
These spots are known as dead spots where sound intensity is so low that it is insufficient for hearing.
This defect can be removed by suitably placing diffusers and reflectors.
Right proportions of internal spaces.
Dead spots.
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42. Dead spots.
Geometrical shape of roof helps in proper distribution of sound
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43. External noise
External noises from vehicles , traffic engines , factories , machines etc. may enter the hall either through the openings or even through walls and other structural elements having improper sound insulation.
This defect can be removed by proper planning of the hall with respect to its surroundings and by proper sound insulation of external walls.
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44. Acoustical design of halls
The initial sound from the source should be of adequate intensity so that it can be heard throughout the hall .
For halls of big sizes suitable sound amplification system should be installed.
The sound produced should be evenly distributed so that there is no dead spots and sound foci.
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45. Acoustical design of halls
The boundary surface should be so designed that there are no echoes or near echoes.
Desired reverberation time should be achieved by proper placement of absorbents on wall.
The out side noise should be eliminated.
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46. Physical Design Principles for halls
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47. Physical Design Principles for halls
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48. Physical Design Principles for halls
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49. Physical Design Principles for halls
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50. Physical Design Principles for halls
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51. Physical Design Principles for halls
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52. Physical Design Principles for halls
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53. Acoustics materials
Carpet is an outstanding sound absorptive material.  When properly selected, carpet absorbs airborne noise as efficiently as many specialized acoustical materials.  No other acoustical material performs the dual role of a floor covering and a versatile acoustical aid.  
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54. Acoustics materials
QUIET BARRIER HD A flexible, 2lb per sq./ft. 1/4 in. thick, high density material with a smooth surface designed to reduce noise transmission between two spaces. Applications include reducing airborne noise transmission through walls, ceilings and floors
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55. Acoustics materials
QUIET BARRIER MD A flexible, 1lb per sq./ft. 1/8 in. thick, high density material with a smooth surface specially engineered to reduce noise transmission between two spaces.
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56. Acoustics materials
QUIET BATT Insulation A premium high-performance acoustical/thermal insulation manufactured from 80% recycled cotton fibers. QUIET BATT® offers superior noise reduction versus typical fiberglass, cellulose and foam insulations
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57. Acoustics materials
Tough core Ceiling Tiles High-performance composite ceiling panel. Especially well-suited to minimize sound transmission between adjacent spaces sharing a common attic space. Available in a variety of finish options and edge details.
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58. Acoustics materials
Isotrax Complete soundproofing system for walls and ceilings. Blocks and isolates sound, reduces noise from traveling through building materials. New or existing construction.
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59. Acoustics materials damping tiles used for noise absorption.
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60. Sound insulation general introduction
Unwanted sound reaching the ears is called NOISE.
It may be due to frequency of sound.
It may be due to intensity of sound .
Or it may be due to the combination of both frequency and intensity of sound.
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61. Sound insulation
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62. Sound insulation general introduction
So sound insulation is the measure by which transmission of sound / noise from inside to out side (vice versa ) or from one room to other is prevented.
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63. Sound insulation ( effects of noise)
It creates discomfort.
It has adverse effect on blood pressure , sleep and causes muscular strains.
It leads to fatigue and decreases the efficiency of a person.
It takes away essence of music and speech.
It disturbs concentration.
Prolonged exposure to noise may result in temporary deafness or even nervous breakdown.
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64. Classification of noise.
From the origin point of view noise may be of two types:-
Out door noise.
Indoor noise.
And noise may also be classified as
Air borne noise or sound
Structure borne noises or impact noises or sounds.
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65. Sources of out door noises.
OUT DOOR NOISES ARE CAUSED BY:-
Road traffic.
Railways.
Climatic conditions.
Aero planes.
Moving machines.
Machines in nearby factories or buildings etc.
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66. 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.
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67. 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.
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68. Acceptable indoor noise level
TYPE OF BUILDING
NOISE LEVEL
IN DECIBLE (dB)
Radios and TV studios dB
Music rooms dB
Hospitals and auditoriums dB
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69. Acceptable indoor noise level
Apartments , hotels and homes dB
Conference rooms , small offices and libraries
Court rooms and class rooms dB
Large public office , banks and stores dB
Restaurants dB
Factories dB
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70. Types of sound insulating materials
Non porous rigid.
Porous rigid materials.
Non rigid porous flexible materials.
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71. Types of sound insulating materials
Non porous rigid
Brick masonry plastered on both sides
Stone masonry structures
Concrete structures
RCC Structures
Porous rigid materials.
Light weight concrete
Cellular concrete
Gypsum board partitions
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72. Types of sound insulating materials
Non rigid porous flexible materials
Perforated boards
Compressed fiber boards
Pulp boards
Mineral wool boards
Acoustic tiles /sheets
Glass wool
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73. Types of sound insulating materials
Non rigid porous flexible materials
Cobalt quilt
Wood wool boards
Curtains
Foams
Celotex boards
Cane fiber etc.
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74. Sound insulating techniques
There are some construction techniques also which are adopted for sound insulation.
Double wall construction.
Cavity wall construction.
False ceiling.
Hollow block construction.
Double pane windows.
Baffle blocks, honey combs etc.
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75. Sound insulating techniques
Double wall construction .
BOARDS
WOODEN STUDS
BOARDS
SOUND ABSORBING BLANKET
WOODEN STUDS
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76. Sound insulating techniques
Cavity wall construction.
EXTERNAL WALL 13MM PLASTERED
5CM CAVITY
BRICK WALL 10CM
CELOTEX OR OTHER INSULATING BOARD
METAL FLY
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77. Sound insulating techniques
False ceiling.
REINFORCED CONCRETE ROOF
SUSPENDERS
FALSE CEILING
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78. Sound insulating techniques
Hollow block construction.
HOLLOW
COMPRESSED CONCRETE HOLLOW BLOCKS
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79. Typical insulation values for different type of walls
Sr. no.
TYPE OF CONSTRUCTION
APPROX.
WEIGHT IN Kg/sq. m
Average TL in dB 1
One brick thick wall that is 20 cm. 50 2
One and half brick thick wall that is 30 cm. 53 3
Cavity wall having two leaves each of half brick thickness with 5cm cavity.
50-53 4
Cavity wall having two 10 cm thick leaves of clinker block with 5cm cavity.
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80. Typical insulation values for different type of walls
Sr. no.
TYPE OF CONSTRUCTION
APPROX.
WEIGHT IN Kg/sq. m
Average TL in dB 5
Half brick wall with 13mm thick plaster on both sides. 45 6
20 cm thick hollow dense concrete block wall with 13 mm thick plaster on both sides.
185 7
Partition wall made with gypsum wall board fixed on timber frame work.
60-70 8
76 mm thick hollow clay block wall with 13 mm thick plaster on both sides. 36
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81. Thank you and enjoy sound
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