1) The document discusses the nature and measurement of sound, including how sound propagates through different mediums as waves. It describes parameters used to measure sound such as pressure, frequency, intensity, and decibel scales.
2) Common sources of noise pollution are discussed, including transportation sources like rail, road, and air traffic. The health effects of exposure to high noise levels are also mentioned.
3) Regulations and ordinances around noise pollution are summarized, including federal laws and more localized approaches. Challenges with enforcement are also noted.
HCL suggests solutions to reduce airborne noise being emitted by vacuum cleaners. It has been seen that blowers used in vacuum cleaners are the main source of airborne noise and blade wakes are unavoidable in turbo machines.Focus of this whitepaper is to understand how to reduce sound intensity of vacuum cleaners and studying its effects on human hearing. ERS division in HCL proposes the design of a spiral enclosure for the blower in the vacuum cleaner. HCL suggests solutions to reduce airborne noise being emitted by vacuum cleaners. ERS division in HCL proposes the design of a spiral enclosure for the blower in the vacuum cleaner.
Determining Typical Ambient Noise Levels in the presence of ConstructionVahndi Minah
Determining ambient noise levels in the presence of construction is a difficult and time consuming task, and the lack of dedicated analysis and visualisation tools can lead to much disagreement between interested parties about typical ambient levels. This paper presents an approach inspired by previous work on cluster-based analysis and visualisation of daily energy usage patterns, and demonstrates substantial success in achieving the aim of establishing typical ambient noise levels, as well as raising further questions about what typical truly means.
hat is Noise Mapping ?
A Noise Map is a map of an area which is coloured according to the noise levels in the area. Sometimes, the noise levels may be shown by contour lines which show the boundaries between different noise levels in an area.
The noise levels over an area will be varying all the time. For example, noise levels may rise as a vehicle approaches, and reduce again after it has passed. This would cause a short-term variations in noise level. In the slightly longer term, noise levels may be higher in peak periods when the roads are busy, and lower in off-peak periods. Then again, there is a greater volume of activity from more people and traffic in the day-time than in the evening or at night. In the longer term, wind, weather and season all affect noise levels.
This means that it is not possible to say with confidence what the noise level will be at any particular point at any instant in time, but where the noise sources are well-defined, such as road or rail traffic, or aircraft, then it is possible to say with some confidence what the long-term average noise level will be.
It may be thought that the best way of doing this is by measurement, but experience shows that this is not the case. For a start, a long-term average must be measured over a long period of time. Secondly, to obtain complete coverage of an area, measurements would have to be made on private property, where access might be difficult, and thirdly, measurements cannot distinguish the different sources of noise, so they would not be able to give information on how much noise was being made by each of the sources in an area.
For these and other reasons, noise mapping is usually done by calculation based on a computerised noise model of an area, although measurements may be appropriate in some cases.
A further benefit of having a noise model is that it can be used to assess the effects of transportation and other plans. Thus the effect of a proposed new road can be assessed and suitable noise mitigation can be designed to minimise its impact. This is particularly important in noise action planning, where a cost-benefit analysis of various options can be tested before a decision is made.
iFluids Engineering
Vivek Mariappan Environmental Engineer Consultant
SoundPLAN CadnaA
Saudi Arabia stands as a titan in the global energy landscape, renowned for its abundant oil and gas resources. It's the largest exporter of petroleum and holds some of the world's most significant reserves. Let's delve into the top 10 oil and gas projects shaping Saudi Arabia's energy future in 2024.
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HCL suggests solutions to reduce airborne noise being emitted by vacuum cleaners. It has been seen that blowers used in vacuum cleaners are the main source of airborne noise and blade wakes are unavoidable in turbo machines.Focus of this whitepaper is to understand how to reduce sound intensity of vacuum cleaners and studying its effects on human hearing. ERS division in HCL proposes the design of a spiral enclosure for the blower in the vacuum cleaner. HCL suggests solutions to reduce airborne noise being emitted by vacuum cleaners. ERS division in HCL proposes the design of a spiral enclosure for the blower in the vacuum cleaner.
Determining Typical Ambient Noise Levels in the presence of ConstructionVahndi Minah
Determining ambient noise levels in the presence of construction is a difficult and time consuming task, and the lack of dedicated analysis and visualisation tools can lead to much disagreement between interested parties about typical ambient levels. This paper presents an approach inspired by previous work on cluster-based analysis and visualisation of daily energy usage patterns, and demonstrates substantial success in achieving the aim of establishing typical ambient noise levels, as well as raising further questions about what typical truly means.
hat is Noise Mapping ?
A Noise Map is a map of an area which is coloured according to the noise levels in the area. Sometimes, the noise levels may be shown by contour lines which show the boundaries between different noise levels in an area.
The noise levels over an area will be varying all the time. For example, noise levels may rise as a vehicle approaches, and reduce again after it has passed. This would cause a short-term variations in noise level. In the slightly longer term, noise levels may be higher in peak periods when the roads are busy, and lower in off-peak periods. Then again, there is a greater volume of activity from more people and traffic in the day-time than in the evening or at night. In the longer term, wind, weather and season all affect noise levels.
This means that it is not possible to say with confidence what the noise level will be at any particular point at any instant in time, but where the noise sources are well-defined, such as road or rail traffic, or aircraft, then it is possible to say with some confidence what the long-term average noise level will be.
It may be thought that the best way of doing this is by measurement, but experience shows that this is not the case. For a start, a long-term average must be measured over a long period of time. Secondly, to obtain complete coverage of an area, measurements would have to be made on private property, where access might be difficult, and thirdly, measurements cannot distinguish the different sources of noise, so they would not be able to give information on how much noise was being made by each of the sources in an area.
For these and other reasons, noise mapping is usually done by calculation based on a computerised noise model of an area, although measurements may be appropriate in some cases.
A further benefit of having a noise model is that it can be used to assess the effects of transportation and other plans. Thus the effect of a proposed new road can be assessed and suitable noise mitigation can be designed to minimise its impact. This is particularly important in noise action planning, where a cost-benefit analysis of various options can be tested before a decision is made.
iFluids Engineering
Vivek Mariappan Environmental Engineer Consultant
SoundPLAN CadnaA
Saudi Arabia stands as a titan in the global energy landscape, renowned for its abundant oil and gas resources. It's the largest exporter of petroleum and holds some of the world's most significant reserves. Let's delve into the top 10 oil and gas projects shaping Saudi Arabia's energy future in 2024.
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This document will discuss each of the underlying technologies to create and implement an e- commerce website.
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Here's a great example: At a large natural gas-fired power plant, where they use waste heat to generate steam and energy, they were puzzled that their boiler wasn't producing as much steam as expected.
R&R and Tetra Engineering Group Inc. were asked to solve the issue with reduced steam production.
An inspection had shown that a significant amount of hot flue gas was bypassing the boiler tubes, where the heat was supposed to be transferred.
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Based on our results, Tetra Engineering installed covering plates to reduce the bypass flow. This improved the boiler's performance and increased electricity production.
It is always satisfying when we can help solve complex challenges like this. Do your systems also need a check-up or optimization? Give us a call!
Work done in cooperation with James Malloy and David Moelling from Tetra Engineering.
More examples of our work https://www.r-r-consult.dk/en/cases-en/
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2. The nature of sound
Sound, a manifestation of vibration, travels in wave patterns through
solids, liquids and gases.
The waves, caused by vibration of the molecules, follow sine functions,
typified by the amplitude and wavelength (or frequency)
Sound waves of equal
amplitude with increasing
frequency from top to
bottom
9. How sound is measured
•Pressure, P, usually Pascals
•Frequency, f, usually Hertz
•Intensity, I, usually W/m2
•Bels, L’, derived from logarithmic ratio
•Decibels, L, derived from bels
P = 1/f
I = W/A
L’ = log (Q/Qo)
L = 10*log (Q/Qo)
E.g. Implications of the decibel scale: doubling sound level
would mean that the sound will increase by 10*log2 = +3dB
Ten times the sound level = 10*log10 = +10dB
11. Reflecting on noise
“Noise" derived from "nausea," meaning seasickness
Noise is among the most pervasive pollutants today
Noise is unavoidable for many machines
We experience noise in a number of ways
environmental
cause and victim
generated by others “second-hand”
Noise negatively affects human health and well-being
The air into which second-hand noise is emitted and
on which it travels is a "commons“, a public good
12. Noise regulation
Noise regulation includes statutes or guidelines relating to
sound transmission established by national, state or
provincial and municipal levels of government. After a
watershed passage of the U.S. Noise Control Act of
1972[1], the program was abandoned at the federal level,
under President Ronald Reagan, in 1981 and the issue was
left to local and state governments. Although the UK and
Japan enacted national laws in 1960 and 1967 respectively,
these laws were not at all comprehensive or fully
enforceable as to address (a) generally rising ambient noise
(b) enforceable numerical source limits on aircraft and
motor vehicles or (c) comprehensive directives to local
government.
13. Local noise regulation
Dr. Paul Herman wrote the first comprehensive noise codes in 1975 for Portland, Oregon with
funding from the EPA (Environmental Protection Agency) and HUD (Housing and Urban
Development). The Portland Noise Code became the basis for most other ordinances for major
U.S. and Canadian metropolitan regions.[18]
Most city ordinances prohibit sound above a threshold intensity from trespassing over property line
at night, typically between 10 p.m. and 6 a.m., and during the day restricts it to a higher sound
level; however, enforcement is uneven. Many municipalities do not follow up on complaints. Even
where a municipality has an enforcement office, it may only be willing to issue warnings, since
taking offenders to court is expensive.
The notable exception to this rule is the City of Portland Oregon which has instituted an aggressive
protection for its citizens with fines reaching as high at $5000 per infraction, with the ability to cite a
responsible noise violator multiple times in a single day.
Many conflicts over noise pollution are handled by negotiation between the emitter and the
receiver. Escalation procedures vary by country, and may include action in conjunction with local
authorities, in particular the police. Noise pollution often persists because only five to ten percent of
people affected by noise will lodge a formal complaint. Many people are not aware of their legal
right to quiet and do not know how to register a complaint
19. Sound and human hearing
People generally hear sounds
between the “threshold of hearing”
and the “threshold of pain”
In terms of pressure,
this is 20 μPa – 100 Pa
The decibel scale was developed from this fact
and makes numbers more manageable
The decibel scale generally ranges from
approximately 0 to 130
22. Sound and human hearing – Frequency
Humans are less sensitive to low frequency
sound and more sensitive to high frequency
sound. Therefore, sometimes the dB scale is
adjusted to take this into account:
A-weighting (db(A)): adjusts overall scale so it
better matches what the human ear would hear
C-weighting (dB(C)): adjusts scale for loud or
low frequency sounds
B-weighting (dB(B)): adjusts by factors that are
“in between” the A-weighted factors and C-
weighted factors (rarely used)
23. The filters used for dBA and dBC
The most widely used sound level filter is the A scale, which
roughly corresponds to the inverse of the 40 dB (at 1 kHz)
equal-loudness curve. The sound level meter is thus less
sensitive to very high and very low frequencies. Measurements
made on this scale are expressed as dBA. The C scale (in dBC)
is practically linear over several octaves and is thus suitable
for subjective measurements only for very high sound levels.
24. Loudness in phons
The phon is related to dB by the psychophysically measured
frequency response. Phons = dB at 1 kHz. For other frequencies,
the phon scale is determined by loudness experience by humans.
25. Loudness in sones
The sone is derived from psychophysical tests where
humans judge sounds to be twice as loud. This relates
perceived loudness to phons. A sone is 40 phons. A
10 dB increase in sound level corresponds to a perceived
doubling of loudness. So that approximation is used in the
definition of the phon: 0.5 sone = 30 phon, 1 sone =
40 phon, 2 sone = 50 phon, 4 sone = 60 phon, etc.
26. Other descriptors of sound
Equivalent sound level – the level of sound that has
the same acoustical energy as does a time-varying
sound over a stated time period.
Percentile sound level – the sound level exceeded “n”
percent of the observation time interval.
Day-night average sound level – the equivalent sound
level for a 24-h period that incorporates a decibel
penalty during night hours.
31. Rail Noise: A Case Study
The city of Ames, Iowa, began operation of three
automated horn warning systems (AHS) in September
of 1998. These systems were installed after nearby
residents repeatedly expressed concerns over the
disturbance created by the loud train horns.
The automated horn system provides a similar audible
warning to motorists and pedestrians by using two
stationary horns mounted at the crossing. Each horn
directs its sound toward the approaching roadway. The
horn system is activated using the same track signal
circuitry as the gate arms and bells located at the
crossing.
35. Roadway Noise
• An example of a “line source” of noise
pollution (as opposed to a “point source”)
• Level of noise is a function of volume,
type of vehicle, and speed
36. Roadway Noise - Solutions
• Regulations limit the amount of noise
some vehicles can produce
• Some regulations require vehicles to be
properly operated and maintained
• Despite regulations, the noise levels are
usually only reduced by 5 to 10 dBA
39. Roadway Noise - Solutions
Pavement type
Certain asphalts, such as those containing
rubber or stone, can be less noisy than other
pavements.
However, some studies have shown the
reduction in noise is only a few decibels, not
enough to be significant.
More research is needed before pavement
type can be an effective noise-reducing
technique
40. Noise contours around
an airport calculated
using INM (Integrated
Noise Modeling) based
on previous noise
measurements
55 - 60 dB = Light blue
60 - 70 dB = Dark blue
70 - 75 dB = Red
75 - 80 dB = Green
80 - 85 dB = Yellow
> 85 dB = Pink
Airport Noise
42. Other sources of noise pollution that
need to be addressed
• Boat noise,
especially jet skis
• Construction noise
• Snow mobiles
• Industry
43. Davis and Masten, Chapter 15
Brüel & Kjær Sound & Vibration
Measurement A/S
Steve J. Gent, P.E., Research Coordinator,
Iowa Department of Transportation
FHWA
References
44. Assignment A2
Please do Problems 15-2, 15-4, 15-8, 15-15 and
15-17
In Davis and Masten, Principles of Environmental
Engineering and Science, Chapter 15.