Sound insulation

1. SOUND INSULATING
MATERIALS
PROF. SANTOSH ALWEKAR

2. Sound insulation –
Sound insulation is the measure by which transmission of
sound/noise from inside to outside or (vice versa) or from one
room to other is prevented.
•Noise definition - Unwanted sound. Due to Frequency of sound ,
intensity of sound or both.
•High frequency sound is more unpleasant than low frequency
sound.

3. Purpose of insulation- to avoid noise
Effects of noise –
• It creates discomfort
•It has adverse effects on blood pressure, mascular strain and on
sleep.
•Leads to fatigue and decreases efficiency.
•It disturbs concentration
•Prolonged exposure – may result in temporary deafness or
nervous breakdown.

4. Noise classification
•Origin point of view–
• Out door noise –Road traffic, railways,aeroplanes etc.
• Indoor noise - Noise caused within the room or from adjacent
room
Alternate classification –
•Air borne noise - Generated in air and transmitted to human air
(Travells through openings such as doors , windows,&
ventilators.
•Structure borne noise – Originate and progress on the building
structure.(foot steps, moving of furniture etc.)
Noise transmission –
1 Through air.
2 By vibrations of structural members
3 Through structural members

5. Sound insulation –
Measure used to reduce the level of sound when it passes
through the insulating building component.
It has a different function than sound absorbent material.
Function of sound insulating material is to reduce the sound
passing through it.
Sound absorbent materials are mostly of porous materials and are
poor sound insulators.
Sound insulating materials are hard materials and are poor sound
absorbers.

6. Sound insulating materials –
•Non porous rigid partitions –
The sound insulation of non-porous, homogenous rigid
constructions such as plastered solid brick masonary wall varies
with the weight per unit area.Every time the weight is doubled
there is an increase in sound insulation of about 4 to 5 dB.
•Porous rigid materials –
The porous rigid materials such as such as porous concrete
masonry.cinder concrete provide 10% higher insulation than the
non porous variety of the same weight. In order to secure the
best insulation from such porous materials,It is recommended
that porous partitions should be plastered at least on one side
and if possible on both sides.

7. •Non rigid or flexible porous materials –
These consists of felt, mineral wool and quilt etcThey provide low sound
insulation as compared to rigid materials therefore they are not generally
usedfor the purpose of noise reduction and isolation.However combination of
rigid materials and flexible porous materials may be adopted.
•Wall insulation – (vertical barriers) –
Walls and partitions are vertical barriers to noise.Their proper design and
construction may insulate the sound to desired level. Three types of wall
construction
1 Rigid and massive homogenous wall- consists of stone,brick or concrete
construction well plastered on both sides.
2 Partition of porous material - The porous rigid materials such as such as
porous concrete masonry.cinder concrete provide 10% higher insulation than
the non porous variety of the same weight.

8. 3 Double wall partition –
It consists of plaster boards or fiber boards or plaster on lath on both the
faces with sound absorbing blanket in between.
4 Cavity wall type construction. –
This is an ideal construction for sound insulation.The gap between the cavities
may be air filled or may be filled with some resilient material like quilt etc.The
two faces of walls may be fixed with celotex or other insulating boards.The width
of the cavity should be atleast 5 cm. and the two wall leaves should be tied by use
of only light butterfly wall ties.

9. •Use of resilient surface material on floors –
This consists of providing thin concrete screed as the R.C.C. floor slab, and
then providing soft floor finish or covering of resilient material such as
Linoleum,insulation board,cork,asphaltic mastic,carpet etc.
•Concrete floor floating construction –
An additional floor is constructed and isolated (floated) from the concrete
floor.Resilient material like quilted mineral or glass wool is laid over R.C.C.
floor.A water proof paper is then laid over it and then 5 cm thk. Concrete screed is
provided .It is important that the concrete should not get through the waterproof
paper.This provides good insulation against impact sounds.

10. Tibmer floor floating construction –
In case of floor constructed of wooden joists,the problem of sound
insulation becomes more difficult, in the present of heavy mechanical impact
sounds.In this a new timber floor is constructed with mineral or glass wool
quilt for isolation purpose.
Timber floor with suspended ceiling and air space
This type helps to improve the insulation of both air borne and structure
borne sounds by isolating them from room below.For solid floors metal
hangersof acoustic clips may be used to support the ceiling below. Floors
and ceilings insulation : Horizontal barriers-
Insulation of floor and ceilings act as horizontal barriers to both air borne
and impact sounds.Rigid construction materials like R.C.C., stones,usedfor
floors and ceilings offer excellent insulation against air borne noise.But the
ydo not function well for impact or structure borne noise
5)Skirting –
The type of skirting fixed will affect the insulation of the floor.An air
gap or a resilient material between the skirting and the floor is used in this
method.Most of the inner portion of the skirting is scooped out to minimize
the contact with the walls.