chapter 5 introduction of noise and noise pollution
TRANSCRIPT
UNIT KEJURUTERAAN ALAM SEKITAR UNIT KEJURUTERAAN ALAM SEKITAR JABATAN KEJURUTERAAN AWAM JABATAN KEJURUTERAAN AWAM
POLITEKNIK SULTAN IDRIS SHAH
CHAPTER 5CHAPTER 5
INTRODUCTION OF INTRODUCTION OF NOISE AND NOISE NOISE AND NOISE
POLLUTIONPOLLUTION
2
Upon completion of this course, student should be able to :
Explain the standard of noise pollution Apply World Health Organization (WHO) standard for
noise pollution Apply Department of Safety and Health (DOSH)
standard for noise pollution Understand the level of noise pollution Explain noise measurement unit (decibel) for noise
pollution Explain the types of noise pollution level Discuss noise pollution criteria Determine sound pressure level and frequency
DEFINATION
Noise Pollution or Sound Pollution, exposure of people or animals to levels of sound that are annoying, stressful, or damaging to the ears. Although loud and frightening sounds are part of nature, only in recent centuries has much of the world become urban, industrial, and chronically noisy.
SOUND Sound is a travelling wave which is an
oscillation of pressure transmitted through a solid, liquid or gas are composed of frequencies within the range of hearing and of a level sufficiently strong to be heard or the sensation stimulated in organs of hearing by such vibrations. In our ears, it gives the sensation of hearing. It is excited by vibrating bodies and transmitted to our ears without sensible motions of the air.
PROPERTY OF SOUND Sound is a disturbance of mechanical energy that
propagates through matter as a wave. Sound is characterized by the properties of waves, which are frequency, wavelength, period, amplitude, and speed.
Humans perceive sound by the sense of hearing. By sound, we commonly mean the vibrations that travel through air and are audible to people. However, scientists and engineers use a wider definition of sound that includes low and high frequency vibrations in air that cannot be heard by humans, and vibrations that travel through all forms of matter, gases, liquids, solids, and plasmas.
Standards of noise pollution
Under the Malaysia Noise Regulation, the prefectural governors have been empowered to designate residential areas, schools of preserving living environment through prevention of noise, while designation such areas prefectural governors shall establish “ regulatory standard” ( maximum permissible level of noise ) for specified hours in respective zones.
Malaysia Environmental Quality Standards for Noise in different areas and for various sources of noise, the maintenance of which is desirable for preservation of the living environment and conductive to the protection of human health are shown in table
Area Code Category Of Area Environmental Noise standards Leq Db ( A )Day Time Night Time
A Industrial Area 75 70
B Commercial Area 65 55
C Residential Area 55 45
D Silence Zone 50 40
Environmental Noise standards
World Health Organization (WHO) standard for noise pollution
Maximum premissible sound level (Laeq) of new development (roads, rails, industrial) in areas of existing high environmental noise climate
Limiting sound level (Laeq) From Road Traffic (For ProposedNew Roads And/Or Redevelopment Of Existing Roads)
Receiving land use category
Day time7 am – 10 pm
Night time10 pm – 7 am
Noise sensative areas low density residential (medium density)
55 dBA 50 dBA
Suburban residential (medium density)
60 dBA 55 dBA
Urban residential (high density)
65 dBA 60 dBA
Commercial, business
70 dBA 60 dBA
Industrial 75 dBA 65 dBA
World Health Organization Standard
Specific Environment
Critical Health Effects LAeq (dBA)
Time Base
(Hours)
LAmax
Fast (dB)
Outdoors living area
Serious annoyance, daytime and eveningModerate annoyance, daytime and evening
5550
1616
--
Dwelling, indoors Speech intelligibility & moderate annoyance, daytime & evening
35 16
Inside bedrooms Sleep disturbance, night-time 30 8 45Outside bedrooms Sleep disturbance, window open (outdoor
values)45 8 60
School class rooms and pre-school, Indoors
Speech intelligibility, disturbance of information extraction, message communication.
35 During class
-
Pre-school bedrooms, indoor
Sleep disturbance 30 Sleeping time
45
Specific Environment
Critical Health Effects LAeq (dBA)
Time Base
(Hours)
LAmax
Fast (dB)
School , playground outdoor
Annoyance (external source)
55 During play
-
Hospital, ward rooms, indoor
Sleep disturbance, night-timeSleep disturbance, daytime and evenings
3030
816
40-
Hospital,treatment rooms, indoor
Interference with rest and recovery
#1
Industrial, commercial shopping and traffic areas, indoors and outdoors
Hearing impairment 70 24 110
Ceremonies, festivals and entertainment events
Hearing impairment (patrons:<5 times / year
100 4 110
Specific Environment
Critical Health EffectsLAeq (dBA)
Time Base
(Hours)
LAmax
Fast (dB)
Public adressess, indoors and outdoors
Hearing impairment 85 1 110
Music and other sounds through headphones/ earphones
Hearing impairment (free-field value)
85 # 4 1 110
Impulse sounds from toys, firework and firearms
Hearing impairment (adults)
Hearing impairment (children)
-
-
-
-
140#2120#2
Outdoors in parkland and conservations areas
Disruption of transquillity #3
#1: as low as possible#2: peak sound pressure (not LAF, max) measured 100mm from the ear#3: existing quiet outdoor areas should be preserved and the ratio of intruding noise to natural background sound should be kept low#4: under headphones, adapted to free-field values
DOSH STANDARD FOR NOISE POLLUTION IN MALAYSIA
Requires factory owner to conduct initial exposure monitoring.
Determine whether any of his employees are exposed to noise greater than the action level of 85 dB(A).
Deviation from such ethical practice may result in the factory owner taking wrong course of action which may lead to unwanted repercussion in the future.
DOSH STANDARD FOR NOISE POLLUTION IN MALAYSIA
To avoid such incident, competent persons must be thorough in categorizing employees in the various occupational groupings and carefully selecting the high risk employee to represent the exposure for the group.
The instrument used must at all-time meet the specified level of accuracy while during monitoring adequate sampling time must be taken to minimize the spasmodic variation in noise level
DEPARTMENT OF SAFETY AND HEALH STANDARD The Factories and Machinery (Noise Exposure)
Regulations 1989 requires factory owner to conduct initial exposure monitoring.
The purpose is to determine whether any of his employees are exposed to noise greater than the action level of 85 dB(A).
Since this is a preliminary requirement to determine further compliance with the employee exposure monitoring requirements, competent person are reminded to conduct the monitoring in all aspect with high degree of professionalism.
Deviation from such ethical practice may result in the factory owner taking wrong course of action which may lead to unwanted repercussion in the future.
The level of Noise Pollution This particular pollution is ever increasing with due
to the rise in the utilization of heavy duty machineries of industrial facilities and vehicles, synonymous to the increase in the standard of living in most countries. We make sounds practically every seconds of our day, but to the extend it has reached an unfavorable high intensity which had cause many disturbances and irritation to others emotionally that has adverse effects on our daily activities.
Noise levels can be measured by decibel method:
Decibel - one tenth of a bell where one bell represents a difference in level between two intensities I1, I0 where one is ten times greater than the other. Thus, the intensity level is the comparison of one intensity to another and may be expressed:
Intensity level = 10 log10 (I1/I0) (dB) For instance, the difference between intensities of
10-8 watts/m2 and 10-4 watts/m2, an actual difference of 10,000 units, can be expressed as a difference of 4 bels or 40 decibels.
These are the few examples of threshold decibels of noises made:
Rustling leaves 20 dB Food blender(3 feet) 90 dB
Quiet whisper (3
feet)30 dB Subway (inside) 94 dB
Quiet home 40 dB Diesel truck (30 feet) 100 dB
Quiet street 50 dB Power mower (3 feet) 107 dB
Normal
conversation60 dB Pneumatic riveter (3 feet) 115 dB
Inside car 70 dB Chainsaw (3 feet) 117 dB
Loud singing (3
feet)75 dB Amplified Rock and Roll (6 feet) 120 dB
Automobile (25
feet)80 dB Jet plane (100 feet) 130 dB
NOISE POLLUTION LEVEL (NPL) A noise measurement procedure recently
introduced in the U.S. in an attempt to relate various earlier studies of community noise. The measurement is conceived so that it combines the ambient noise level with the degree of steadiness in time of the noise (assuming that the less steady it is, the more distracting and annoying it becomes). The basic definition is:
LNP = Leq + ko
where Leq is the equivalent energy level measured in dBA or PNdB, k is a constant which is provisionally given the value 2.56, and k is the standard deviation of instantaneous levels in time. This measurement system applies to any environment, unlike those specifically concerned with aircraft and traffic. As a result, however, it is incapable of determining whether the noise being measured is wanted or unwanted sound.
A measure of sound pressure level, given the symbol L. Various subscripts define the nature of the measurement, most commonly as follows
L10: sound level exceeded 10% of the time (peak level)
L50: sound level exceeded 50% of the time (average or mean level)
L90: sound level exceeded 90% of the time (ambient level) LA: sound level in decibels measured on the A scale
Leq : equivalent energy level LNP : noise pollution level
DECIBEL The decibel is widely known as a measure of sound pressure
level, but is also used for a wide variety of other measurements in science and engineering: acoustics, - to quantify sound levels relative to a 0 dB reference
which has been defined as a sound pressure level of .0002 microbar, or 20micropascals
Electronics - to express power or amplitude ratios (gains), control theory other disciplines.
SOUND LEVEL METER
Method of Sound Measurement
• The test must be done at noisy area.• Make sure that the area is on planning guidelines
noise limits and control• Set up the microphone 1.2-1.5 metre from the ground.• Keep away the microphone from any structure that
can reflected the sound at least 3.5 metre.• The SLM reading is depends on:
rain wind electronic object
HISTORY OF DECIBEL
The decibel originates from methods used to quantify reductions in audio levels in telephone circuits.
Named the "bel" in honor of the Bell System's founder and telecommunications pioneer Alexander Graham Bell.
The bel is seldom used, as the decibel was the proposed working unit.
NOISE POLLUTION LEVEL Noise pollution level (Lnp) is a method to make
noise assessment without knowing the source of the noise.
Produce according Leq, Leq is a equivalent continuous sound pressure level .
The formula of noise pollution level is :Lnp = Leq + Ko
o : Standard deviation sound level that time.K : Constant (value : 2.56)
The formula can also be summarize as :
Lnp = Leq + ( L10 - L90 )Where :Leq shows the level of energy sound and (L10 – L90)Shows the suitability of disturbance that causesfrom fluctuation of noise level
NOISE POLLUTION CRITERIA
Frequency, or its inverse, the periodWavelengthWave numberAmplitudeSound pressureSound intensitySpeed of soundDirection
Wavelength The distance between any point on a
wave and the equivalent point on the next phase. Literally, the length of the wave.
Amplitude
The strength or power of a wave signal. The "height" of a wave when viewed as a graph.
Higher amplitudes are interpreted as a higher volume, hence the name "amplifier" for a device which increases amplitude.
Frequency
The number of times the wavelength occurs in one second. Measured in kilohertz (Khz), or cycles per second. The faster the sound source vibrates, the higher the frequency.
Higher frequencies are interpreted as a higher pitch. For example, when you sing in a high-pitched voice you are forcing your vocal chords to vibrate quickly.
Sound Pressure Sound pressure or acoustic pressure is the local
pressure deviation from the ambient (average, or equilibrium) atmospheric pressure caused by a sound wave. Sound pressure in air can be measured using a microphone, and in water using a hydrophone. The SI unit for sound pressure p is the pascal (symbol: Pa).
Sound pressure level (SPL) or sound level is a logarithmic measure of the effective sound pressure of a sound relative to a reference value. It is measured in decibels (dB) above a standard reference level.
Sound Intensity
In physics, intensity is a measure of the energy flux, averaged over the period of the wave. The word "intensity" here is not synonymous with "strength", "amplitude", or "level", as it sometimes is in colloquial speech. For example, "the intensity of pressure" is meaningless, since the parameters of those variables do not match.
To find the intensity, take the energy density (that is, the energy per unit volume) and multiply it by the velocity at which the energy is moving. The resulting vector has the units of power divided by area (i.e. W/m²). It is possible to define the intensity of the water coming from a garden sprinkler, but intensity is used most frequently with waves (i.e. sound or light).
The Speed of Sound
A sound wave is a pressure disturbance that travels through a medium by means of particle-to-particle interaction. As one particle becomes disturbed, it exerts a force on the next adjacent particle, thus disturbing that particle from rest and transporting the energy through the medium. Like any wave, the speed of a sound wave refers to how fast the disturbance is passed from particle to particle
Sound Pressure Level and Frequency
The frequency (f), which is the number of pressure variation cycles in the medium per unit time, or simply, the number of cycles per second, and is expressed in Hertz (Hz). Noise is usually composed of many frequencies combined together. The relation between wavelength and frequency
Frequency
Defined as the difference in sound pressure entering and will
be detected by the ear. Pressure level variations per second
is called frequency. Frequency of vibrations per second the
number one center or the number of complete revolutions
per second and in depthwith the unit hertz (Hz). Sound
produced are different in frequency. At low frequency the air
particle vibrate slowly produces a ‘bass’. While at high
frequency of air particle vibrate rapidly which produces a
‘soparno’ ( barben 1976 )
Sound pressure level Source of energy flow in a pressure of sound waves
is generally more suitable for use in measuring the noise level (SPL) compared with the volume. sound pressure generated in the space depending on the content of the acoustic space. sound produced in a confined space will have many differences compared to that produced in the open air. sound pressure does not directly depend on the source but also on the environment. distance of the sound pressure in real life is very broad.
since the relationship between the volume is proportional to the field that links the sound pressure sound pressure level (SPL) can be described in the following logarithmic
SPL = 20 log10 (p/ Pref ) dB
In which P : sound pressure produced in
the unit decibel (dB)
Pref : racial reference at the threshold of human hearing out of 2 x 10-5 N/m2
measurement of sound is dependent on the above formula for the rate of different sound pressure level at different conditions in terms of sound output and environmental impact.
Level - weighted sound pressure level A, B, C and D Type - type of weights are:
Units of dB (A): the extent of 55 dB sound pressure
Units of dB (B): the sound pressure between 55 and 85 dB
Units of dB (c): high sound pressure
