Acoustics

1. CONSTRUCTION TECHNIQUES FOR SOUND INSULATION
BY : FAROOQHPASHA.A |USN: 1BQ15AT026 | BS-IV | SEC-7A | BMSSA
INTRODUCTION:
The structural elements and their construction for controlling noise in
buildings are mentioned below.
CONSTRUCTIONOF WALLS FOR SOUND INSULATION IN A
BUILDING :
Wall are an important structural elementin all kind of buildings, that
provides protectionfrom the noise externally as well as internally. The
usage of differentwall materials or the usage of differentdesignforthe
wall would bring variation in the insulating properties of
the element.
The figure below shows the difference in sound attenuation with
variation in wall design.
The methods employed fornoise control in buildings are explained in the
following:
1. Wall Massand the Thickness are Increased
The massiveness of a material is an efficientparameter that resists
noise. Hence concrete walls are more insulating than wooden walls.
Another way of increasing the insulating property is to add more
thickness for the walls.
The increase of thickness of walls would result in more mass which in
turn increase insulation. A reduction of 6 decibelsound happens by this
method of construction. But the techniques must be carried out keeping
in mind the costand economy.
Wall constructionthat undergoes vibration under huge frequenciesof
sound has to be avoided.

2. CONSTRUCTION TECHNIQUES FOR SOUND INSULATION
BY : FAROOQHPASHA.A |USN: 1BQ15AT026 | BS-IV | SEC-7A | BMSSA
Fig.1. Different Wall Design Techniques Showing the Variation of
Sound Attenuation
2. Use of Cavity Partition in Buildings for Noise Control
The sound transmission can be resisted by the usage of airspace
between the two partition walls. The air space can also be placed in
between two or more layers. This conceptis more effective than a single
wall of equal weight, which is found to be more economical.
3. Increase Airspace Width of Walls
The increase in airspace will obviously increase the noise insulation
property. But the huge increase in the width of air space is difficultto
designand consumes more space.
4. Increasingthe Stud Spacing
It is found by a study that the spacing betweenthe studs would increase
the sound transmission capacity of the room. Say an increase of 2 to 5
decibelSTC is determined fora stud spaced 24 inches than those
spaced at 16 inches.

3. CONSTRUCTION TECHNIQUES FOR SOUND INSULATION
BY : FAROOQHPASHA.A |USN: 1BQ15AT026 | BS-IV | SEC-7A | BMSSA
5. Usage of Studs in a Staggered Manner
The arrangement of studs in a staggered manner as shown in figure-1,
where studs are placed alternatively would help in noise absorption, thus
reducing noise intensity.
Fig.2. Figure Shows Variety of Wall Types, their Cost Comparison and
STC Values
6.Studs and Panels held together by Resilient Materials
Making use of inexpensive resilient layers like glass or fibre board, or
semi-resilientattachments which are inert in nature, will help in reducing
the STC rate by two to five decibels.
7. Panels Used are Dissimilar
Using different thickness and materials for panels would help in
reduction of noise, thus increasing the sound insulating quality of walls.
8.Sound AbsorbingBlanketsUsed in the Airspace
The sound absorbing blankets are also called as isolation blankets
which are placed in the airspace arrangement, that are provided
between the panels. This blanket enables an increase in sound
attenuation.

4. CONSTRUCTION TECHNIQUES FOR SOUND INSULATION
BY : FAROOQHPASHA.A |USN: 1BQ15AT026 | BS-IV | SEC-7A | BMSSA
Mineral or rock wool, wood fibres or fiberglass are some the materials
used to make these blankets. These blankets have an attenuation
capability up to 10 decibels.The method is more effective where
lightweight construction is more prominent.
9.The Cracksand Edges are Sealed
The full advantage of a high-performance wall can be brought out only
when it is properly sealed and crack free. The perimeterof the wall must
be properly sealed.
Formation of cracks or holes would affectthe insulation property of the
wall. It has been observed that a hole of the 1-inch square will result in a
reduction of STC of the wall by 10.
Fig.3. Depicts Before and After the Sealing of Cracks
Construction of Windows for Acoustic Control in Buildings
Windows are one of the weakest elements of a building. Their
inappropriate position or opencondition would affectthe performance of
insulating walls. Therefore,it is recommendedto have acoustical
considerationin the arrangement of windows.

5. CONSTRUCTION TECHNIQUES FOR SOUND INSULATION
BY : FAROOQHPASHA.A |USN: 1BQ15AT026 | BS-IV | SEC-7A | BMSSA
The graph below shows the variation of STC values of the wall, for the
differentarea occupied by the windows which are shown in percentages.
The following measures can be employed to reduce the noise
entering the building through the windows:
1.Windows can be Closed
Permanent sealing or closing of the windows are the best
measures to reduce the direct effect of noise. Permanent
sealing becomes essential when an air conditioning system
must be enabled. So, sealing acts as a constant solution for
noise.
The masking of noise is an effect that is facilitated by the air
conditioning system, which is discussed in the following topics.
2. Windows Size can be Reduced
The loss of contribution of total partitions can be reduced by
making the window size to small. Small windows do have
certain other advantages like:
o Expensive acoustic windows can be excluded

6. CONSTRUCTION TECHNIQUES FOR SOUND INSULATION
BY : FAROOQHPASHA.A |USN: 1BQ15AT026 | BS-IV | SEC-7A | BMSSA
o Usage of glass is reduced
The method faces certain disadvantages too. The decrease of
window size is limited, as the window size should follow certain
rules and regulations. Its decrease by, say from 50 to 20 %
would only bring up a change of 3 decibels.
3. Glass Thickness can be Increased
The more thickness the glass gains, the more resistant towards
the noise. If sealing is not desired, the glass thickness can be
increased. Further, the glass can be laminated with a tough
plastic, which is transparent in nature. This is both shatter and
noise resistant.
ConstructionofDoors for Acoustic Control in Buildings
Doors are considered very difficult to handle than windows,
acoustically. Replacing a hollow core door by a solid door is one
of the solutions. This is found relatively expensive.
The sound insulation can be increased if at the bottom and at
the top, a drop bar or gasket stops are installed. Another
solution is to reduce their use in walls facing noise directly.
Install doors on the wall that is shielded.
ConstructionofFloors for Acoustic Control in Buildings
Special acoustical treatment is the only way to reduce the
vibration of floors due to heavy noise. Installing a heavy
concrete floor or using a floating floor is some of the treatment
methods.
Floating floor involves using a concrete or wooden slab over the
existing one, which is separated by a resilient material.
Noise Control in Buildings by use of Masking
This method involves the drowning of noise with the help of a
background noise. This is effective during noise fluctuations.
Masking can be created by soft music, electronic devices or air
conditioning systems and heating systems.