Assignment 3 Sound - Construction Technology 5

This assignment discusses acoustic construction solutions, air-borne sound transmission, structure-borne sound transmission, and discontinuous construction in the context of construction technology. It provides explanations, diagrams, and examples to understand the concepts better.

Assignment 3 Sound
Construction Technology 5 (Envelope) Semester 1, 2019
Hassan Mansour
17687023

Table of Contents
Question 1 – Acoustic Construction Solutions.......................................................................................2
Question 2 – Air-Borne Sound Transmission.........................................................................................6
Question 3 – Structure-Borne Sound Transmission...............................................................................8
Question 4 – Discontinuous Construction...........................................................................................10
Question 5 – Auditorium Design..........................................................................................................11
References...........................................................................................................................................13

Question 1 – Acoustic Construction Solutions
Using diagrams list and explain three ways that construction design solutions are used to reduce
noise at the source.
The ability to understand and recognize sound waves via pressure fluctuations and vibrations
through organs called ears is the definition of the term hearing. An individual must have an
understanding of the auditory science field on an elementary in order to understand the role played
by the acoustics in constructions industries especially within the design stage.
The ears of human beings are known to be electro-acoustic transducer which simply means that ears
sense the alterations in air pressure. By converting the detections into electric impulses,
communication reaches the brain. The brain generally classifies sounds into two; the first sound is
called monotonous. The monotonous sound is known to be inconspicuous and never interferes with
the human attention in case the unsynchronized tick clock sound could affect concentration and lead
to discomfort.
Ears are unique creations in their construction. The ear has a complex structure that is developed to
direct the sound waves coming and convert them into the brain's language. The ear is divided into
three parts the air filled middle and outer and the fluid-filled inner component.
Figure 1. Shows the structure of the human ear
The outer part of the ear is known as the concha which channels sound waves inside especially
wavelengths of over 9mm. this leads to higher sensitivity to greater sound pitch than low sound
pitch. The Eustachian tube also is known as the auditory canal balance the air pressure between the
middle and outer ears for processing to the eardrum. Symptoms of pain which includes a reduction
in air planes are reasons behind imbalanced pressure in the auditory canal. Yawning and swallowing
can help relieve such pressures.
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The eardrum is found in the middle ear and has 3 very tiny stones inside the body called stapes,
incus and malleus. The eardrums are responsible for vibrations coming in and magnify them to
enable the fluid-filled inner ear to detect any sensations.
Figure 2. An illustration of vibrations being converted into electric impulses by the eardrum
The oval window separates the inner ear from the middle ear. The oval window is connected to the
stapes and at a higher intensity vibrates compared to the ear drum leading to the pulsating of the
inner ear fluid. The pulses lead to the investable swaying of the 25,000 hairs spread along the
cochlea which stimulates the nerve endings linked to the hairs. For a fact, the cochlea has an organ
called the otolith which has the responsibility of bringing balance.
The composition of the ear is very fragile and delicate as discussed above, hence, causing probable
deficiencies because of old age and subjection to deafening illnesses or sounds. It is vital to
implement successful and corrective construction solutions for acoustic when it is still at the design
stage of development.
When identifying methods to better the conditions of acoustic it is important to determine the
sources of noise and then deploy the means of reducing the noises. External sources of noise are
grouped into 3 as follows; traffic, residential and industrial sources of noise. The various real
solutions in minimizing noise at the source are:
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1) Setting the noise source in an enclosed soundproof area
The most used and successful soundproofing is usually done through heavy construction. In heavily
constructed materials, there is an added mass structure which will impede the resonating sound
from the source. The barrier's effectiveness rests on the properties of the materials as well as the
method of construction used. For example, wing walls are used in increasing the acoustic shadow in
the area that the building will be put up.
Figure 3 above shows the wing walls
2) Noise source positioning
On the other hand, one can opt to put up an isolated enclosure in that the noise source will be
positioned in a place good in acoustic noise reduction as well as absorption. Take the illustration of
the lift shaft that is made In between walls with mass or the service rooms that have acoustic
soundproof walls through the use of absorbing liners, floor dampers and walls with high mass.
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Figure 4 above shows a demonstration of strategic noise source placing
3) Noise source isolation
Thirdly, a method that is most feasible, between the three noise source isolation from structures
involves setting up flexible connections or plant feet with the acoustic rating between the structure
and the noise source thereby decreasing the intensity of vibration as well as the structure's noise.
Figure 5 above shows the flexible isolation connections
An important note between the three option mentioned above is the need to endure that the source
of noise is not able to resonate at a similar frequency to the structure or support. The ability to
distinguish these frequencies lies on being able to reduce the intensity by addition of mass to the
source of noise thereby adding the sound's inertia from the resonating source.
Materials that have high rigidity and mass perform best when counteracting the noise from their
respective sources. These types of materials include masonry or concrete which are great in
absorbing vibrations. One mostly used acoustically relating material is the structural concrete that
exists as in-situ floors or walls. These walls or floors are able to be improved by increasing their
thickness hence increasing the mass quantity. This result in an added acoustic rating for the
respective structure.
Timber is another material that is selectively used since it enables bouncing off of sound thereby can
be able to achieve a good balance. This is the reason why most instruments' framework is from
timber. Metals can also be used. Metals, for example, steel, are better soundproof materials but are
not widely used since they have a pricy purchasing value. Their market is inflated compared to
concrete.
The latest state of the construction industry involves treating acoustics as an important part of
building and noise reduction since there is a dedicated process of procuring within the industry
regarding noise prevention. The magnitude of noise generation is being monitored. Acoustic reports
are being produced using specialized engineers who with time are looking to develop different
products apart from the invented insulation blankets, pipe lagging and insulation boards that are at
least 50 mm thick with double the concrete's acoustic rating.
1)
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Question 2 – Air-Borne Sound Transmission
In a diagram explain some of the pathways for flanking sound transmission in building the
structure. How is this best dealt with?
A world with no fixtures and openings on its insulated walls, services and fittings are looking to
become the easiest problem when opting to solve acoustic problems. However, if a building does
not have these types of services, the building will be rendered not purposeful and useless. The term
flanking entails sound waves resonation due to inability to penetrate a structure’s main insulation,
hence, the waves tend to re-direct towards weak points around the structure. The weak pints
include service outlets, air gaps and penetrations.
Figure 6 shown above displays the flanking scenario
The transmission of sound through flanking is broadly put into two types. These include structure-
borne transmission as well as air-borne transmission. In this paper, concentration is going to the air-
borne type of transmission together with the required methods prevention. In areas that are at least
colder, the techniques of preventing flanking become easier compared to buildings that are built in
locations with humid climates which should be regularly circulating with fresh air.
Sound transmission through the air has numerous sources that include music, speech, series and
vehicles. The purpose of the use of acoustics solutions intends to impact the weak points within
acoustic components when providing complete sealing. Using resilient tapes and gaskets are some
of the mostly implanted tactics that completely make the areas airtight for mounted services such as
mechanical or plumbing equipment.
In penetrating structural element that includes electrical lights, outlets, doors and windows, it is not
advisable to use some materials that include concrete or steel. Therefore, there are different types
of materials used, for example, caulking, insulation wool or engineered boards. These better
operating materials increase the acoustic capability of the components used in framing the building
such as floors and walls.
One more method entails offsetting the power points located in between the stud cavities in the
walls as displayed below. This restricts air penetration to a minimum. Additional use of rubber seals
help in adding air leak reduction, the area becomes airtight.
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Figure 7 shown above displays the stud wall offsets.
Offsetting and overlapping sheets of plasterboards on both sides of erected walls gives a better
technique that helps in reducing leakage of air as well as preventing transmission of sound through
air.
Figure 8 shown above displays the overlapping joints in plasterboards.
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Question 3 – Structure-Borne Sound Transmission
Why is structure-borne sound transmission often a problem in older residential apartment blocks?
Give an example.
The prevention of sound transmission through the air only solves half of the issues. One additional
issue that needs solving is the transmission of sound through structures. This can be defined as
structure-borne transmission whereby sound is able to travel through the applied elements in
structured walls, floors and ceilings.
Similar to the previous discussion, increasing the structural mass of elements used would lead to an
added acoustic properties of the referred component. In mass slaw, in any increase n unit are mass
to a factor2, leads to a loss in transmission by 6dB.
Take this example into perspective. An average office's environment or in any normal conversation
has a rating of 60 dB (use the table presented below) as well as a brick wall having a 220mm
thickness, would possess a rating amounting to 50dB. This means that the referred wall is able to
take in 50db of the normal conversation that is happening on the opposite side. Therefore, the
structure-borne sound transmission is being reduced by to only 10dB. This rating when compared to
the Australian government, can match the faint breathing sound production.
Sound
level (dB)
Loudness approximation in
relation to ordinary
conversation.
Perceived example
0 Nothing is audible Hearing threshold
10 1/32 loudness Very faint normal breathing
20 1/16 loudness Quiet room
30 1/8 loudness Quiet office interior/ Quiet conversation
40 ¼ loudness Quiet rural area/ Moderately quiet office
50 1/2 as loud Next room with running dishwasher/ Quiet
suburban area/
60 Ordinary conversation Ordinary conversation /Average office
70 Double loudness 3m apart vacuum cleaner/Loud busy street
80 4 times P3m apart passing car/ Noisy office
90 8 times 3m apart passing truck or bus/Intensely heavy
traffic
100 16 times 3m apart passing subway train/ loud car horning
110 32 times Band playing in a night club/ Pop group
120 64 times An extremely loud jet taking off at 100m
In accordance with the BCA, the preferred RW limitations for floors or walls between dwellings that
adjoin are listed in the table drawn below.
Structure Rw Requirement (Min)
Floors on dwellings 50
Adjoining kitchen, bathroom or laundry walls as well
as a habitable room in adjoined dwellings
50
Other walls 45
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The conventional methods of construction that are mostly used within the modern-day construction
techniques, not used in developing older blocks of apartments are numerous. However, one new
technique for construction is used in walls as displayed in the figures below.
Figure 9 shown above displays a modified acoustic wall type with a required RW50
There are internal walls like the one mentioned above which contain better-improved materials for
insulation such as fire and bats protective plasterboards that could not be accessed in the past. The
most used technique in older buildings are structures made up of hard coverings or laundry, kitchen,
living rooms and bathroom areas. The hard coverings used in floors are able to be put up without
using protective barriers in acoustic in this modern-day code used in Australia for building.
Older apartments' structure-borne transmission would have their blocks in big problems if there
missed being an advancement in their acoustic properties. These buildings have been improved in
terms of acoustic capabilities. All these improvements have become a reality due to the
government's enforced code on the minimum required acoustic levels in buildings.
Floors, walls and ceilings were previously affected by structure-borne transmission of sound due to
their old and outdated acoustic designs. For example, they had continued internal walls, door jambs
and window trims that had air gaps and the hard floor covering made of concrete slabs or steel
frames.
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Question 4 – Discontinuous Construction
Describe an example of discontinuous construction being used to reduce sound transmission in
buildings.
The widely used technique in multi-residential dwellings makes use of the discontinuous
construction methods which help in reducing the transmission of sounds within the building on a
large scale. In these discontinues constructions, there are 2 completely erected separate wall
structures which lack connections or any kind of penetration between the identified wall structures.
This technique helps provide acoustic resistance in a stud wall, producing a similar result as a double
brick wall. However, the stud wall is more economical during installation.
Figure 10 shown above displays a discontinuous type of wall.
Combining 4 major construction details gives a determination of the success in discontinuous types
of walls. Looking at figure 10 shown above, there exists a clear cavity between 2 walls. In this cavity,
the dimension should be at least 50mm wide so that there is an achieved RW rating as per
regulations. However, the cavity can be enhanced by installing insulation batts.
A similar effect can be produced by using coincident dips. Discontinuous construction can reduce the
noise intensity by avoiding resonance in a similar frequency as seen by installing barriers. For
example, a stud wall discontinuously mounted having an identical thickness becomes vulnerable
coincidence since it has uniform thickness and mass. The flow of vibration has to be disrupted. This is
achieved by installing barriers with a variety of thickness on both sides of the wall. These
discontinuous walls are mostly used in walls dividing dwelling places such as between apartments
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Question 5 – Auditorium Design
Using diagrams explain some of the principles of auditorium design for live theatre.
Room acoustic analysis is hard since, during designing, the size, shape and space location is
considered. Space may be absorbent or reverberant. Also, the echo, sound source and reverberation
effects, sound quality are considered during design.
Auditorium space is a theatre's section that hosts the audience and is categorized as reverberant
space since it is enclosed. Reverberation entails perpetually reflected sound from walls or floors. The
reflection is progressive until it depletes its energy. Reverberations measured in reverberation time
which is the duration for that 60dB of sound takes to disperse.
Figure 11 shown above displays the reverberance paths
Wallace Sabine in 1895 derived a formula that relates to reverberation time allowing the
reverberation time manipulation by either subtracting or adding a space’s mass. The mass could be a
person or a cushion.
RT =0.16 V
A ,W h ereV =Volume of space ∈m3
A=Absorbance of space ∈m2
Space in the auditorium could influence the sound in that too little space may dull the sound or
much bigger pace could make the sound lucid. Therefore the optimum considered reverberation
time is between 0.5 to 1 second. The auditorium's shape also has an effect in that when long the will
be echoes like London's Banqueting house which echoes from its long halls. Hence, reducing the
path of sound or delay speaker installation at the auditorium' back.
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Mismatching walls and using absorptive material prevents the standing wave effect due to too
rectangular spacing as echoes are stopped. Additional space fanning reduces resonance and brings
the audience near the stage. Relative to space and shape, auditorium surface may reflect or absorb
sound and thee two properties need to be combined. When absorbent materials such as cushion
line the walls and reflective materials such as metals make up the theatre as shown in the figure
below are used, the sound is distributed evenly.
Figure 1 - Auditorium Layout
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References
Milne, G., Banfield, K. and Reardon, C. (2013). Noise control | YourHome. [online] Yourhome.gov.au.
Available at: http://www.yourhome.gov.au/housing/noise-control [Accessed 22 May 2019].
Berendt, R., Winzer, G. and Burroughs, C. (1967). A guide to airborne, impact, and structure-borne
noise-control in multifamily dwellings. Washington: U.S. Dept. of Housing and Urban Development.
Pohl, J. (2011). Building Science: Concepts and Application. 1st ed. United Kingdom: John Wiley &
Sons, pp.147-224.
Szokolay, S. (2014). Introduction to Architectural Science: The Basis of Sustainable Design. 3rd ed.
United Kingdom: Taylor & Francis Ltd, pp.222-260.
Australian Building Codes Board (2016). NCC Volume One. Canberra ACT 2601: The Australian
Building Codes Board, pp.176-177.
Bevan, D. (2013). Sound Transmission
Bevan, D. (2013). Sound & Hearing.
Module 8 Mechanics of Hearing. (2011).
Module 9 Noise Control. (2011).
Module 10 Room Acoustics. (2011).
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