1. ENVIRONMENTAL ENGINEERING
NOISE POLLUTION

2. Definition Noise is defined as unwanted signal.
To be more specific, noise is referring to unwanted sound.
But, sometimes the word “unwanted” can be subjective.
Two type of noise pollutions:
a) Voluntary noise
b) Involuntary noise

3. Classification of Sound
Continuous
-An uninterrupted sound level that varies less than 5 dB during
the period of observation.
-Example: Noise from household fan
Intermittent
-A continuous sound that last for more than one second but then
interrupted for more than one second.
- Example: A dentist’s drilling
Impulsive/Impact
-A sound which last for less than one second.
-Example: Noise from firing a weapon

4. Effect of Noise
Reduction of quality of life; i.e. interfere speech, conversation and sleep.
Physiological effects, i.e. hearing effects.
Psychological effects, i.e learning effect, mental health

5. Source of Noise Noise can be emitted from:
A point source – electric fan
A line source – moving train

6. Source of Noise Noise pollution comes from: Traffic
Industrial equipment
Construction activities
Sporting & crowding activities
Low-flying aircraft.

7. Noise Control
The level of noise can be reduce by using one of three strategies
1- protect the recipient
2- Reduce Source of Noise

8. Noise Control 1- protect the recipient
Using ear plugs for ear protection is not effective for most of noise types. Thus , better to protect the entire ear and protect the ear plugs wearer from the most noise

9. Noise Control 2- Reduce Source of Noise
The most effective means of noise control is source reduction.
Re-design of commercial airplanes has already been mention as an example of noise source reduction.

10. Noise Control For traffic noise
Reduction can be achieved via re-designing vehicles and pavements.
Increasing the use of alternative transportation
Reducing vehicle speed and encouraging to use alternative routes, through speed control devices or road designs

11. Sound Power
Sound power (W): the rate at which energy is transmitted by sound wave.
Sound Intensity (I): Average sound power per unit area normal to propagation of a sound.
W = ∫A I dA ….. (1)

12. Sound Power
In an environment, in which there are no reflecting surface, the r.m.s. sound pressure, Prms at any point is related to I by following equation:
I = P2rms / ρc ….. (2)

13. The Decibel
Human ear able hear enormous range of sound pressure. (20 μPa to 1013 for normal people).
Therefore, sound pressure of linear scale is an inconvenient quantity to use.
This also applied to sound power and sound intensity.

14. Sound Pressure Level, Lp
Sound pressure level, Lp is defined as
Lp = log10 (P2rms/ P2ref) Unit : Bel …..(3)
Or,
Lp = 10 log10 (P2rms/ P2ref) Unit : (dB) …..(4)
Pref = 20 μPa.
The factor 10 is introduced in above equation as to avoid a scale that is to compressed.

15. Lw = 10 log10 (W/ Wref) Unit : (dB) …..(5)
Sound Power Level, Lw
Sound power level, Lw is defined as:
Lw = 10 log10 (W/ Wref) Unit : (dB) …..(5)
where;
Wref = Watt

16. Sound Intensity Level, LI
Sound Intensity Level, LI is given by:
LI = 10 log10 ( I/ Iref) Unit : (dB) ….. (6)
where;
Iref = Watt/m2

17. Example 3-1
The sound pressure inside a diesel lorry is 2 Pa. What is corresponding SPL in dB?
(Answer: 100dB)

18. Example 3-2 If a sound source has a pressure of 1500 Pa, compute:
The SPL in dB
The sound intensity in Watt/m2
Given;
ρ = kg/m3 , c = 340 m/s

19. Example 3-3
What is the increase in dB that corresponds to a five time increase of sound pressure?

20. Environmental Engineering
Engineering Decision

21. Objectives Description of Technical Analysis Decision
Cost Effectiveness Analysis Decision
Benefit /Cost Analysis Decision
Risk Analysis Decision
Environmental Impact Analysis Decision

22. Engineering Decision
Decision Based on Technical Analysis 1- Assumption should be made for first stage since the technical analysis will be vary EX. SW trucks A and B have sufficient capacity to haul the waste only operation and maintenance cost might be very different.

23. Engineering Decision
Design basd on Cost Effectiveness Analysis 1- compare the cost of different alternatives based on a- Annual cost : annually operating facility cost b- present worth: the funds needed to construct the facility.

24. Engineering Decision
Decision Based on Benfits/ Cost Analysis convert most of the facility items to monetary items. Check which items are giving some benefits in comparison with remaining items.

25. Engineering Decision Decision Based on Risk Analysis
-Define the type and source of pollutant
Identify the pathways & rate of exposure. How can it get to human and cause health problem
Decide what impact is acceptable what effect is considered

26. Engineering Decision
Estimate the maximum allowable emission or discharge.
if the emission or discharge higher than the maximum allowable, determine what technology needs to achieve max allowable emission or discharge

27. Engineering Decision
Decision Based on Environmental Impact Ananalysis EIA report has to be prepared , report include: 1- Inventory Data gathering in this stage such as biological, chemical and physical data. This stage doesn’t include any discussion. Collecting Data will be implement for assessment level

28. Engineering Decision 2- Assessment
Assessment mechanism will estimate the following:
Importance of the impact.
Magnitude of the impact.
Nature of the impact.

29. Engineering Decision
3-Evaluation Last stage is evaluation stage where conclusion and recommendation will take place here. The final conclusion and recommendation will be built in base of the inventory and assessment steps.