ENVIRONMENTAL ENGINEERING NOISE POLLUTION

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

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

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

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

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

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

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

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.

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

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)

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)

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.

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.

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 = 10-12 Watt

Sound Intensity Level, LI Sound Intensity Level, LI is given by: LI = 10 log10 ( I/ Iref) Unit : (dB) ….. (6) where; Iref = 10-12 Watt/m2

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

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 = 1.185 kg/m3 , c = 340 m/s

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

Environmental Engineering Engineering Decision

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

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.

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.

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.

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

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

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

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

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.