1. ARCH 4320 - Environmental Systems in Architecture
lecture 4 : Acoustic
Transmission Loss (TL)- noise reduction
Instructor:
Dr. Eng. Nagham Ali Hasan
3rd semester
2019-2020
University of Palestine
College of Applied Engineering & Urban Planning
Department of Architecture
1
Reference: http://www.primacoustic.com/document-type/installation-guide/
6. VIBRATION INSULATION
• to diminish the propagation of the vibration
energy by isolating the machine from the
building frame using elastic building elements
6
7. • The background noise levels in recording studios,
listening rooms, concert halls, and other acoustically
sensitive spaces must be minimized if these rooms are to be
used in their intended way.
• Approaches to Noise Control
There are five basic approaches to reducing noise in an
acoustically sensitive space:
• Locating the room in a quiet place.
• Reducing the noise output of the offending source.
• Interposing an insulating barrier between the noise and the room.
• Reducing the noise energy within the room.
• Both airborne and structure borne noise must be considered.
8.
9.
10.
11.
12. Sound-Insulating Windows
• If a window is placed in the wall between a control
room and studio, or in a wall facing loud outdoor
ambient sound levels, the window’s sound
transmission loss should be comparable to that of the
wall itself.
13. Noise barrier
A noise barrier (also called a soundwall, , sound barrier, or acoustical barrier)
is an exterior structure designed to protect inhabitants of sensitive land
use areas from noise pollution.
Noise barriers are the most effective method of mitigating roadway, railway,
and industrial noise sources – other than cessation of the source activity or use
of source controls.
13
14. Basic Design Principles
14
a row of street trees may
appear to form a solid
line.
The horizontal wall configuration
can be designed to create
spaces which are commonly
referred to as negative spaces or
forms
Noise barrier would appear
massive and overpowering
located adjacent to a back lot
line.
15. Noise barrier
A concrete stack barrier with planting pockets
A vertical stacked concrete pipe barrier well integrated
into a domestic setting with planting
A stack barrier using coated steel pockets fixed to
a steel frame
A fully vegetated concrete crib system provides a large
verdant screen
16. Barrier should be placed as
close to the road as possible on flat
or elevated ground
Barrier should be placed at the
top of the cutting slope
Noise barrier walls
Is made of absorptive material mitigate sound differently than those that are a
hard surface.
19. Noise in buildings
Building layout and design
Noise levels vary through different times of the day, so it
is worthwhile to try and take account of when noise is,
or might be, generated.
- Locate quiet rooms as far away from noise sources as
possible, without compromising passive solar design
principles.
- Install windows away from noise sources if possible and
select sound absorbing types.
- Locate noisy areas together and away from quiet areas.
- Avoid putting laundries, bathrooms or living rooms next
to, above or below bedrooms without adequate sound
insulation. Consider mounting noisy appliances on
sound absorbing pads.
- Accommodate teenagers by providing extra
soundproofing for their rooms and locate them away
from adult living and sleeping areas, and neighbours.
19
21. 21
Approaches to Noise Control
There are five basic approaches to
reducing noise in an acoustically
sensitive space:
1. Locating the room in a quiet
place.
2. Reducing the noise output of the
offending source.
3. Interposing an insulating barrier
between the noise and the room.
4. Reducing the noise energy
within the room.
5. Both airborne and
structureborne noise must be
considered.
23. 23
Structureborne Noise
• vibration from outside traffic
• HVAC (heating, ventilating, and air
conditioning) units,
• the impact of footsteps in a distant part
of a building
• Water pipes and plumbing fixtures,
Structureborne noise
is most efficiently
controlled at the
source of the noise.
24. • Structureborne noise is thus most efficiently controlled at
the source of the noise.
• Massive, rigid partitions such as concrete walls are most
useful for attenuating airborne noise, but offer little
resistance to structureborne noise.
On the other hand,
• lightweight materials offer little protection against airborne
noise, but can be used to decouple elements of structures,
and are thus effective against structureborne noise.
24
32. Transmission Loss (TL)
• Transmission loss (TL) is the loss in sound power that results
when sound travels through a partition. TL is the loss as sound
passes through a barrier.
• The more power that is lost, the greater the TL.
• TL values range from about 10 to about 80 dB.
32
τ= 90%
34. • TL defined as: difference between sound pressure level
(SPL) on the source side of the barrier, and the SPL on the
receiver side:
34
The higher the TL value, the greater the attenuation provided by a material.
35. •
معين تردد عند االنتقال فقد
ه
و
مقاسا االنخفاض مقدار
بالديس
بل
انت أثناء الصوت يعانيه الذي
قاله
الفاصل خالل
35
the transmission coefficient ( τ ) , the amount of sound
that passes through a material where:
τ = 1 − α
هو
الفاصل عن تعبر التي الصوت قدرة بين النسبة
wt
به المصطدم
wc
منه اآلخر الجانب في لتشع الفاصل تعبر التي الصوت وقدرة بالفاصل والمصطدمة بالهواء المولدة الصوت قدرة بين النسبة هو أو
• We relate τ to TL as:
τ= wt/ wc
TL= 10 log 1/τ dB
for example, a glass fiber material might have a high absorption coefficient of 0.9 at 500 Hz
which would yield a τ of 0.1, that is, (1 − 0.9 = 0.1). And TL of the glass fiber would be 10, that
is, 10 log (1/0.1), which is quite poor.
41. Comparison of Wall Structures
• the effective sound transmission loss performance of the
• composite construction will fall below that of the most
effective single component and approach that of the weaker
• element.
• For example, assume a 200-ft2 section of a 4-in.
• brick wall has an average TL of 40 dB.
• If a 7 × 3 ft pass door having an average TL of 25 dB is cut
into the brick wall, the effective TL of the composite wall
can be found
• as follows:
41
48. Sound-Insulating Windows
• Improving the sound insulation of
a double glazing window can be
achieved by:
- Having the widest possible cavity
between panes of glass
- Using thicker glass
- Differing the thicknesses of the
two glass panes used
- Using an efficient insulating
window frame
- Using specially laminated
acoustic glass
• It can also be incorporated within
double glazing window ranging in
thickness from 26mm - 40mm, as
well as single glazed applications
from 6.8mm to 12.8 mm in
thickness. 48
