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AIR QUALITY AND POLLUTION (TKA 3301) LECTURE NOTESUNIVERSITY MALAYSIA TERENGGANU 2009Disclaimer: I don't own this document. If you believe you do, and you don't want it to be published here, please let me know. I will remove it immediately.
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Dr. Marzuki Hj. IsmailDr. Marzuki Hj. Ismail
Semester I 2009/10 Semester I 2009/10
ENTECHENTECH
Sound is caused by pressure variation Noise – unwanted sound Noise – environmental pollutant
Health effects of noise
2 kinds of health effects of noise non-auditory effects and auditory effects
Non-auditory effects = Stress, Physiological and behavioural effects, and Safety concerns.
Auditory effects = Acoustic trauma, Tinnitus, THL(TTS), PHL(PTS)
PersekitaranPersekitaran Paras Leq* Paras Leq* maksimum maksimum
yang yang dibenarkan, dB dibenarkan, dB
(A)(A)
KesanKesan
Perindustrian/Perindustrian/PekerjaanPekerjaan
7575 Kerosakan Kerosakan pendengaran pada pendengaran pada
paras tinggiparas tinggi
Masyarakat/Masyarakat/Bandaran (siang)Bandaran (siang)
5555 Kerunsingan Kerunsingan bertambah pada bertambah pada
paras tinggiparas tinggi
Masyarakat/Masyarakat/Bandaran (malam)Bandaran (malam)
4545 Kesukaran untuk Kesukaran untuk tidur pada paras tidur pada paras
tinggitinggi
Domestik (siang)Domestik (siang) 4545 Kesukaran Kesukaran berkomunikasi pada berkomunikasi pada
paras tinggiparas tinggi
Domestik (malam)Domestik (malam) 3535 Kerap terjaga dari Kerap terjaga dari tidur pada paras tidur pada paras
tinggitinggi
Levels and DecibelLevels and Decibel
Low range = 0.00002 Pascal High range = > 200 Pascal
0
' logQ
QL
L’ = levels, belQ = measured quantityQo = reference quantityLog = log in base 10
0
log10Q
QL Decibel (dB)Decibel (dB)
Adding 2 sound and equivalent sound cannot be simply added or average arithmeticly
This is cause sound level are measure based on logarithm
There are 3 method to add sound pressure which is by using Formulate, Schedule or Chart
Combine Sound Level Pressure
FORMULATE This method based on Formulation:
10
1
10log10
iLni
iPL
Lp = Sound power level n = no of sound pressure level
SCHEDULESCHEDULE This method involve adding sound pressure This method involve adding sound pressure
based on Decibel Increment Schedule based on Decibel Increment Schedule (below)(below)
Different between 2 sound level need to be
added (dB)
Value need to be added to the highest value (dB)
0 – 1 3
2 – 4 2
4 – 7 1
7 – 10 0.5
Over 10 0
Solution is as below:
The more precise method is the Formulate method. Schedule (and Graph) method are used because it faster
The different can be ignored because as long as the calculation is correct, your answer can be accepted
The same can be used for 3 sound:
GRAPHGRAPH
This method is almost the same as the Schedule method in the way sound are added
In Schedule method, a schedule are used meanwhile for this method, a graph are you for the addition
The graph is as shown:
Eg:
What sound power level results from combining the following 3 levels: 68dB, 79 dB, and 75 dB?
Day-Night Sound Level - Day-Night Sound Level - LdnLdn is the A-weighted equivalent sound level for a is the A-weighted equivalent sound level for a 24 hour24 hour period period
with an additional with an additional 10 dB10 dB imposed on the equivalent sound imposed on the equivalent sound levels for night time hours of levels for night time hours of 10 p.m10 p.m. to . to 7 am7 am..
Day-Night Sound Level can be expressed asDay-Night Sound Level can be expressed as
where where Ldn = day-night sound level (dB)Ldn = day-night sound level (dB) Ld = daytime equivalent sound level (dB) Ld = daytime equivalent sound level (dB) Ln = nighttime equivalent sound level Ln = nighttime equivalent sound level
(dB)(dB)
Equivalent Sound Level – Equivalent Sound Level – LLeqeq
Quantifies the noise environment as a single Quantifies the noise environment as a single value of sound level for any desired duration. value of sound level for any desired duration.
Equivalent Sound Level - Equivalent Sound Level - LLeqeq - can be expressed - can be expressed asas
where where n = total no. of samples takenn = total no. of samples taken LLii = noise level in dBA of the ith = noise level in dBA of the ith
samplesample ttii= fraction of total sample time= fraction of total sample time
Eg: 1
A noise level of 90dBA exists for 5 min. and is followed by a reduced noise level of 60dBA for 50 min. What is the equivalent continuous equal energy level (Leq) for the 55 min period?
Eg: 2
Calculate equivalent continuous equal energy level (Leq) for a residential area in KT?
Time (h) Sound Level (dBA)
0000-0600 42
0600-0800 55
0800-1000 65
1000-2000 70
2000-2200 68
2200-0000 57
Good LuckGood Luck
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