• General discussion on effects of sound
• Types of Noise
• Transmission of noise
• Sound Insulation vs. Sound Absorption
• Transmission loss
• Maximum noise levels
• Means of noise control and sound
GENERAL DISCUSSION ON EFFECTS OF
High noise conditions not only result in
uncomfortable living conditions, fatigue,
inefficiency and mental strain, but prolonged
exposure to such conditions may cause
temporary deafness or nervous break-downs.
Sound-proofing is absolutely essential in case of
film studios, radio-broadcasting stations,
television stations, sound recording studios etc.
The insulation of noises is important for office
buildings , hospitals , educational institute ,
Though it is difficult to prevent the outdoor noises
coming into the building but acceptable indoor
noise levels can be achieved by adequate
planning of building and its components and by
suitable constructional measures using
TYPES OF NOISE
‘Noise’ is defined as unwanted sound. Noises
from their origin point of view are of the
following two types:
1. Outdoor Noises.
2. Indoor Noises.
1. Outdoor Noises: These noises have their
source of origin outside the room or building,
such as rood traffic, railways, aero-planes,
lifts, loud speakers, moving machinery in the
neighborhood or in adjacent buildings.
2. Indoor Noises: These noises have their
source of origin inside the room or building, such
as conversation of the occupants, foot steps,
banging of doors, shifting of furniture, in water
closets, working of typewriters, playing of radios,
Another Classifications: From the viewpoint of the
analysis of sound insulation problems, the
noises are again classified into two types:
1. Air-borne Noises or Sounds.
2. Structure-borne Noises or Impact Noises or
1. Air-borne Noises or Sounds: It is
generated in the air and is transmitted through
the air directly to the human ear. This types of
sound travels one part to another through small
gapes or openings or by vibrating the partition
walls or doors.
2. Structure-borne Noises or Sounds:
They are originate and progress in the building
structure. It is caused by impact and transmitted
as air-borne noises.
TRANSMISSION OF NOISE
The noise is transmitted in the following 3 ways.
1. Through the air.
2. By the vibration of Structural Members.
3. Through the Structural Members.
type of noise transmission, being common is
type becomes prominent only when the
enclosing walls, floors, ceilings etc. are of thin
type is prevalent where mechanical vibrations
are caused, particularly in case of factories, work
shops, public buildings, offices etc.
SOUND INSULATION vs. SOUND
The distinct function of sound absorption is the
prevention of reflection of sound waves where
as the function of sound insulation is the
prevention of transmission of sound, may be by
any means. Sound insulation is used to indicate
the reduction obtained when sound passes from
one room to another room or from one side of
partition to the other side.
Porous materials, which are generally good sound
absorbents, are poor sound insulators and vice
During transmission of air-borne sound from the
source to the recipient; a reduction in the sound
intensity takes place and this is termed as
‘Transmission Loss’. This transmission loss is
numerically equivalent to the loss in the intensity
of sound expressed in decibels (i.e., dB).
The following facts regarding transmissions loss
require special attention:
1. The efficiency of sound insulation of any
barrier, such as partition, wall, floor etc. is
expressed in terms of the transmission loss of
that occurs while the sound is being transmitted
through the barrier.
2. The transmission loss or sound insulation
offered by a structure depends upon the
materials used and the method of construction
3. Transmission loss varies directly with the
frequency of sound.
4. Higher sound insulation of a barrier is indicated
by the larger transmission loss.
MAXIMUM ACCEPTABLE NOISE LEVELS
The maximum level of noise which will neither
annoy the occupants nor damage the acoustics
of the building is termed as acceptable noise
level inside the building.
Some maximum Acceptable noise levels:
Hospitals – 40-50 dB.
Class rooms or lecture rooms - 45-50 dB.
Residential buildings – 45-55 dB.
Factories – 60-65dB. etc.
MEANS OF NOISE CONTROL AND
It have been laid by the Indian Standard (Is: 1952-
1962) for various types of buildings.
Some example of sound insulation between
Between houses or flats: 40 dB.
Between one room and another in the same house
or flat: 30 dB.
Between lecture rooms: 40 dB.
Between 2 wards in hospital: 30 dB . etc.
The study of noise control and sound insulation can
be further divided in the following heads:
1. General consideration.
2. Constructional measures of noise control and
3. Practical hints and conclusions.
1. General consideration: The following
general considerations should be made for
noise control and should insulation in buildings.
1. The 1st
and foremost way of insulating against
air-borne noise is to isolate it at source. Air tight
rooms for machinery would achieve this purpose to
some extent. Working methods, which create
less noise, can be adopted.
2. The residential buildings should be properly
located in a quite area away from the noisy
surroundings. The building should be properly
oriented with respect to the road and it should
be such that doors and windows do not face
the source of noise.
3. The different units of a building should be
4. The provision of furnishing material and lining
of walls and ceilings by means of air-filled
materials, helps to reduce the noise to a great
5. The transmission of noise by vibrations can be
prevented by making the walls, floors, partitions
very rigid and massive or heavy.
6. The control of impact sound to some extent is
possible by either providing resilient materials
or to carry the whole floor surface on resilient
7. Structure-borne noise or sounds can be
Constructional Measures of Noise
Control and Sound Insulation
by introducing discontinuities in the path of
vibrating waves and by using sound absorbing
8. The personal protective devices, such as
earplugs, head-phones etc can be used to
reduce the noise to the extent of 20 to 30 dB.
1. Walls and partitions.
2. Floors and ceilings.
3. Windows and doors.
4. Insulating sanitary fillings.
5. Machine mounting or insulations of machinery.
1. Walls and partitions: these wall
constructions should act as vertical barriers in
the transmission of air borne sound or noise.
To achieve this objective, the following
methods of wall construction can be adopted
depending upon the extent of sound insulation
i. Rigid and Massive Homogeneous Partitions.
ii. Partitions of Porous Materials.
A composite Construction employing a
combination of rigid materials and porous
absorbers can be adopted with advantage of
better insulation with lesser unit weight of
iii. Hollow and Composite Partition Walls or
Double wall Constructions.
2. Floors and Ceilings: The objective of
floors and ceilings construction should be to
offer adequate insulation against impact sound.
The objective can be met by the following
i. Use of Resilient Surface Material on
Floors: By this method, insulation against
impact noises to an extent of 5 to 10dB over a
bare concrete floors can be obtained.
ii. Providing a Floating Floor
Construction: The principle underlying the
construction of a floating floor is its insulation
from any other part of structure.
Floating floor construction can be adopted for both
concrete as well as wooden floor.
i. Concrete Floor: It is 5 types.
a. Concrete Floor with Floating Concrete Screed.
b. Concrete Floating Wood Raft.
c. Concrete Floor with Suspended Ceiling and
Soft Floor Finish or Covering.
d. Concrete Floor with Light Weight Concrete
Screed and Soft Floor Finish or covering.
e. Heavy Concrete Floor With a soft Floor Finish
ii. Wooden Floors: It has 2 types.
Type 1. when Supporting walls are 10cm thick or
Type 2. When Supporting Walls are 20cm thick or
We can also use of Suspended-ceiling with Air-
3. Windows and Doors: In case of windows,
sound insulations of single windows is
improved by making them as air-tight as
possible by filling the air space at the edges of
such panes with sound absorbing material.
In case of doors, the transmission loss or sound
reduction increases with the increase in weight.
4. Insulating Sanitary Fittings: For improved
insulation, water-closets should not be fixed
above a living room or next to a bed room
unless the latter is well-insulated, as for
example by cup-boards etc.
5. Machine Mountings or Insulation of
Machinery: The machines or mechanical
equipments create vibrations is an adjoining
building and are transmitted further away as
structure-borne sound, the machines should be
insulated by resting them
on resilient supports or mountings such as steel
springs, rubber, cork etc.
3. Practical Hints and Conclusions:
i. From view point of noise control, when
windows of bed or living rooms face a main
traffic route or a railway line, they should not be
situated less than 30 to 45 m from its near
ii. The increase in transmission loss or sound
reduction of a solid massive construction is
slow in proportion to the increase in its
iii. If the material used is of porous and flexible
nature, like hair felt, its sound reduction is
proportional to its thickness.
iv. In double wall or cavity wall construction, an
air-space is generally better than a filling
v. A cavity wall with two leaves having thickness
of 10cm each, has 80% increase in insulation
value as compared to a single brick solid wall
of 20cm thickness without any increase in
weight but with a little increase in cost.
VI. Smaller and solid glass panes have better
insulation property as compared to larger and
thicker flexible glass panes.
VII.Double glazing of glass windows improves
insulation to a considerable degree.
VIII.Sealed double windows or triple windows of
plate glass with an air-space in between can
be successfully used where sound-proofing is
IX. A steel plate door is more efficient for sound
insulation than a double wall, hollow cold
X. The desired sound insulation or sound
reduction can be achieved in any one or more
of the following 3 ways:
a. By adopting continuous construction by using
homogeneous materials where sound
reduction depends upon the weight per square
b. By adopting semi-discontinuous construction
where air-cavities are employed with cross-
connection between the two partitions. These
cross-connections should be few in number and
preferably made of flexible material.
c. By adopting a fully discontinuous construction
where there is complete discontinuity in the
structure by means of an air cavity or an elastic
acoustic materials. This method is considered
suitable for meeting the requirements of sound
insulation of the highest order within the
reasonable weight per square metre.