Noise Pollution PDF

Sound Transmission of sound waves Physics of Sound Sound is a form of energy that can be heard by human beings Sound is ge...

Sound Transmission of sound waves Physics of Sound Sound is a form of energy that can be heard by human beings Sound is generated by a vibrating object and transmitted by Longitudinal wave pressure variations through a medium (solid, liquid or gas) A wave vibrating parallel to the Example direction of its propagation Wavelength (‫)ג‬ Two kinds of wave Transverse wave Period (T) When the drum surface A wave vibrating at right angle Frequency (f) vibrates, it causes slight (perpendicular) to the direction changes in air pressure of its propagation Amplitude (A)/Intensity These changes in air pressure Speed of sound travel as waves through the air Sound propagates as longitudinal waves (also called compression or other medium and produce the sound waves), not transverse waves It requires a medium (solid/liquid/gas) to propagate Striking a drum surface with a stick Wavelength (‫)ג‬ Period (T) Frequency (f) T Time required for one complete cycle Distance from a particular point on a wave to the next point that is at of the wave to pass by a point T The rate of vibration per unit the same height, going in the same direction Distance = Time taken by a wave to travel a distance of one wavelength time measured in cycle Tim Time e λ 1 As the frequency of a wave A Frequency (f) = ) increases, the time period of the wave y( Period (T) Distance Wave velocity () n o T Wavelength (‫= )ג‬ it Tim e Frequency (f) A decreases is Time The unit of frequency is Po Hertz (Hz) Distance Position Distance (x) The unit for time period is A Wavelength is measured in 1 Hz = 1 wave per second “second” meters A Formula for period: λ T = 1/f where T = period and f = frequency Human can perceive sounds in the range from ~ 20 Hz to 20 kHz Amplitude (A) Speed of sound Inaudible Audible Inaudible A Distance ) It is the distance between the origin and y( n o Time it SOUND crest (or trough) is Po Tim e It is the distance travelled by a sound wave per unit time as it 20,000 It represents the pressure intensity and Hertz (Hz) 20 200 2,000 A propagates through any medium is related to the volume or loudness Low-pitch High-pitch Ultrasounds A larger amplitude means a louder Sound waves move through the medium (solids, liquids or gases) Infrasounds sounds Medium sounds sound, and a smaller amplitude by vibrating the molecules in the matter (Base means a softer sound sounds) Dogs (> 50,000 Hz) Amplitude is measured in meters dB Bat (> 100,000 Hz) Speed of sound depends on composition/density of media Speed of sound in various substances Short summary: the physics of sound Sound waves move through the medium (solids, liquids or gases) by vibrating the molecules in the matter Speed of sound in various media: Speed of wave: < < Particles generally far apart so Particles are much closer than Particles closely packed so that the wave travel further before those in air. They can quickly the wave travels even faster they bump into one another. transmit vibration energy from than it does in either liquid or Due to less resistance to one particle to the next. The air. But a lot of energy is Source: http://www.sengpielaudio.com/calculator-wavegraphs.htm movement of particle, less sound wave travels > 4 times required to start the wave at the energy is needed to start the faster than it is in air, but it takes beginning wave, but the wave will not a lot of energy to start the travel fast vibration Short exercise Short exercise Measurement of sound level Name the properties of sound (1) – (3) in the following figures: Loudness of sound can be measured in terms pf decibel (dB) Which wave has the higher frequency? 2 Decibels are measured on a logarithmic scale 1 A 3 When a sound increases by 10 units on the decibel scale, its loudness becomes 10 time B more powerful A small change in the number of decibels results in a huge change in the amount of noise and the potential damage to a person’s hearing Noise Noise level and daily limits of exposure Sources of noise pollution = Unwanted or unpleasant sound that potentially results in Noise level (dB) Daily time limit for exposure Examples Environmental noise is the accumulation of all noise present in a specified (without hearing protection) annoyance and/or hearing loss environment > 130 Reaching the threshold of pain Firecracker 120 Dangerous even for a short period of time Disco music From the point of view of physics, noise is indistinguishable from sound – Both arise 115 < 1 minute Rock concert from vibrations that happen through a medium Household sources From domestic gadgets 109 < 2 minutes Car horn From entertainment Difference between sound and noise arises when the brain receives and perceives a Air-conditioner 106 3.75 minutes Video game centre Indoor noises equipment sound 103 7.5 minutes Toy gun Crying baby TV Noise perception is subjective 100 15 minutes Music through earphones (Highest volume setting) Factors such as the magnitude, characteristics, duration and time of occurrence may 94 1 hour Music through earphones (Mid to high affect one to think whether a sound is a noise. volume setting) 91 2 hours Electrical drill 85 8 hours Vacuum cleaner Moving of furniture Vacuum cleaner Source: “Bridge”, Issue No. 43 (2009), Department of Health Conversation of the inhabitants  Sources of noise pollution Sources of noise pollution Effects of noise pollution Construction Transportation Social events Traffic Noise Celebration and entertainment events Effects of noise pollution generally depends on: Events that use loudspeaker Commercial and industrial activities Etc… Industrial machines Intensity of noise (How loud) Duration of noise exposure (How long) Pumping system Frequency of the exposure (How many Air-conditioning times during the day exposed to such a noise) Aircraft Noise Business-related machines such as refrigeration systems Etc… Adverse effects of noise pollution on health Adverse effects of noise pollution Fundamental of noise control Hearing damage Permanent hearing loss can result from prolonged exposures to sound levels of > 85 dB Mental stress High blood pressure 1. Identify the sources of noise Higher sound intensities require much less time to cause damage Sleep disruption 2. Recognize the noise sensitive receptors and potential impact Being on the landing field without ear protection where jet planes are disembarking could cause measurable hearing losses in less than an hour Distraction 3. Avoid the noise Noise can also result in a temporary threshold shift which is a reversible hearing Productivity loss 4. Mitigate and reduce the noise loss normally lasting from moments to hours, although longer periods of Effects on communication temporary hearing loss are possible Irritability and headache Very loud explosions or gunfire can cause acoustical trauma which can rupture or damage eardrums and middle ear bones etc... Source-based noise control Sources of noise pollution Path-based noise control Personal habits To avoid the production of noise or to reduce the noise level To control noise at the transmission pathway It is cost-effective and easier to implement Quieter working methods or technologies Examples: Designing and fabricating silencing devices in aircraft engines, automobiles industrial machines and home appliances Maintenance/ replacement of the noisy machines Legislation Examples: Temporal and geographical restrictions of noisy heavy vehicles Restrictions for the time of construction works  Installation of noise barrier Adding insulation and sound-proofing barrier Distance attenuation to cut down noise by zoning urban areas Sound-proofing material Reflected noise Transmitted noise X Noise OR Noise cancellation by absorbing or reflecting back (blocking) the sound wave energy Reflected noise Absorption https://www.epd.gov.hk/epd/noise_education/young/eng_young_html/m3/m3.html Receiver-based noise control Receiver-based noise control Summary: Fundamentals on noise control To mitigate or reduce the noise at the receiver end To protect the receiver Installation of noise barrier Noise proof enclosures Noise cancellation devices Distance attenuation Depriving the receiver of an “open-window” Reduction of exposure time etc. “The noise path”, https://www.youtube.com/watch?v=8Cq5UR5KssA Planning against noise nuisance Noise control by the Hong Kong Government Planning Example Key considerations when planning against noise nuisance Relocation of Airport (in 1998) Will the proposed development be sensitive to noise? Kai Tak Airport was located in the city Will the proposed development create noise? 1. Planning centre and surrounded by residential Are there any noise sensitive receivers (e.g., schools, hospitals etc.)? 2. Abatement buildings About 380,000 people were affected by What extent of the noise impact (level and exposure time) 3. Legislation noise of up to 100 dB from aircraft less How the noise can be avoided or reduced? 4. Partnership than 100 meters overhead The airport was relocated to Chek Lap Kok in 1998 Today, the no. of people affected by the severe aircraft noise is about 200 Source: https://www.epd.gov.hk/epd/noise_education/young/eng_young_html/m4/m4.html  Planning Abatement Abatement Example Example Example Roads are re-surfaced with noise absorptive Setting up road-side noise barriers or enclosures materials which help to reduce traffic noise up to Paving roads with low-noise resurfacing materials 5 dB Implementing traffic management scheme, such as Podium deck Noise absorptive restricting or diverting traffic at certain sensitive hours. materials are standard features of all new highways. Source: https://www.epd.gov.hk/epd/noise_education/young/eng_young_html/m4/m4.html Source: https://www.epd.gov.hk/epd/noise_education/young/eng_young_html/m4/m4.html Legislation Legislation Legislation Noise Control Ordinance Cap. 400 (NCO); enacted in 1988 Noise Control Ordinance Main legislation on noise To provide statutory control to restrict and reduce the nuisance caused by noise Any person who Road Traffic Ordinance To provide control over noise generated from newly- commits an offence registered motor vehicles Specifically it controls over noise from: under the Ordinance Domestic premises and public places (general neighborhood noise) shall be liable to the Civil Aviation (Aircraft To provide control over aircraft noise (Stringent noise standards following maximum have been set for aircrafts arriving at and departing from the Construction activities (e.g., piling) Noise) Ordinance Hong Kong International Airport Places other than domestic premises, public places (noise from industrial or penalties: commercial premises) Intruder alarm systems (installed in any premises or vehicles) Factories and Industrial To control occupational noise generated inside the factory or other industrial activities which affects the employees working Individual items of plant or equipment (referred to in the Ordinance as Product Undertakings Ordinance in these workplaces Noise) (Enforced by Labour Department) Motor vehicles (requiring noise emission from motor vehicles to comply with stringent international standards on the first registration in Hong Kong) Source: https://www.epd.gov.hk/epd/noise_education/web/ENG_EPD_HTML/m3/ordinance_7.html#1 Partnership Noise control in Hong Kong Construction noise Construction noise is a huge problem in Hong Kong Construction noise To train and educate the operators in various sectors (e.g., the construction industry, restaurant trade, vehicle repair workshops Traffic noise The Noise Control Ordinance came and property management sector), which are affected by pollution Aircraft noise into effect in 1989 and included control laws, through partnership programmes controls on construction noise that Neighborhood noise have been progressively tightened Noise from industrial and commercial activities Figure adapted from EPD Construction noise is mainly controlled under a construction noise permits and noise emission labels  Construction noise permit Statutory controls on construction noise applicable to different Control on percussive piling operations at different times Construction noise permit must be obtained from EPD for either of the following two situations: Construction noise permit must be obtained from EPD for either of the following two situations: Using specified powered mechanical equipment or carrying Using specified powered mechanical out prescribed construction work in Designated Areas, or equipment or carrying out prescribed carrying out general construction work using powered construction work in Designated Areas, or mechanical equipment, from 7 pm to 7 am on weekdays, and carrying out general construction work using powered mechanical equipment, from any time on Sundays and public holidays 7 am to 7 pm on weekdays, and any time on Sundays and public holidays Carrying out percussive piling from 7 am to 7 pm on any Carrying out percussive piling from 7 am to Piling day other than a public holiday 7 pm on any day other than a public holiday Figure adapted from https://www.epd.gov.hk/epd/english/ greenconstruction/poll_pro/piling.ht ml Source: https://www.epd.gov.hk/epd/english/laws_regulations/enforcement/resource_enfor4.html Source: https://www.epd.gov.hk/epd/english/environmentinhk/noise/data/highlights_en_pro_hk.html Noise emission labels Control over traffic noise Aircraft noise The Noise Control Ordinance provides the control of noise Installing roadside barriers and resurfacing existing roads with low-noise from hand-held percussive materials breakers and air compressors Eliminating the noise problems at the outset through planning Breakers that weigh more than Managing vehicle under the Noise Control (Motor Vehicles) Regulation, which 10 kilograms and air stipulates that new vehicles for use in Hong Kong must meet European Union compressors that can supply and Japanese noise control standards before registration compressed air at 500 kilopascals or above must be Providing soundproofing facilities to more than 10,000 school classrooms near fitted with noise emission major roads labels when being used for Aircraft noise is monitored by the Civil Aviation Department and quieter practices such as construction work Imposing restrictions on noisy large vehicles from heavily built up residential noise abatement procedures during take-off are required areas during the night and the periodical or temporary blocking of some roads to Hand-held percussive breaker Air compressor traffic Source: https://www.epd.gov.hk/epd/misc/ehk06/eng/text/e07.02.html Neighborhood noise Noise from industrial and commercial activities Factories and commercial operators generate noise Noise from domestic premises and public places Regulated under the Noise Control Ordinance (NCO) It is restricted under the Noise Control Ordinance, as is neighborhood noise Examples of noise from domestic premises Examples of noise from public areas Source: https://www.epd.gov.hk/epd/sites/default/files/epd/english/environmentinhk/noise/guide_ref/Dealing%20with%20Noise%20Nuisance.pdf