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					                                         Noise pollution


1. Introduction
     Noise is an unwanted sound. Especially when very loud, it becomes a form of pollution
   because it is irritating, causes mental stress and may even lead to temporary or permanent
   deafness. The loudness (intensity) of sound is measured in decibels (dB). The scale goes
   from 0dB which is total silence to 200dB which would be measured next to a rocket taking
   off. Noise mainly comes from four sources: (a) aircraft noise, (b) road transport noise, (c)
   construction and industrial noise, and, (d) neighborhood noise. The problem generated by
   noise is not only that it is unwanted, but also that it negatively affects human health and
   well-being. In Hong Kong, noise generated in working areas is controlled by the Labour
   Department while noise generated in other places is controlled by the Environmental
   Protection Department.
                              Sound Levels and Human Response


                Common sounds                Noise Level (dB)            Effect


         Rocket launching pad (no ear
                                                   180          Irreversible hearing loss
                  protection)
           Carrier deck jet operation
                                                   140               Painfully loud
                 Air raid siren
                  Thunderclap                      130
               Jet takeoff (200 ft)
                                                   120          Maximum vocal effort
                Auto horn (3 ft)
                  Pile driver
                                                   110              Extremely loud
                 Rock concert
                 Garbage truck
                                                   100                 Very loud
                  Firecrackers
              Heavy truck (50 ft)                                   Very annoying
                                                    90
                 City traffic                                   Hearing damage (8 Hrs)
               Alarm clock (2 ft)
                                                    80                 Annoying
                  Hair dryer
                Noisy restaurant
                Freeway traffic                     70          Telephone use difficult
                Business office
             Air conditioning unit
                                                    60                 Intrusive
             Conversational speech
           Light auto traffic (100 ft)              50                   Quiet
                  Living room
                   Bedroom                          40
                  Quiet office
                    Library
                                                    30                 Very quiet
              Soft whisper (15 ft)
Broadcasting studio   20
                      10    Just audible
                      0    Hearing begins
2. Sources
   (a) Aircraft noise
          The old airport (Kai Tak International Airport located in Kowloon City) is closer to
       the city than any other major airports in the world. People living there are heavily
       affected by the aircraft noise. Whenever take-off and landing, the noise produced can be
       very damaging and annoying. Even at mid-night, the noise level is still around 80dB
       which is sufficient to affect sleeping.



                                          Landing of aircraft
                        [Source: http://home.netvigator.com/~thomast/pollution]



                  [Source: R. B. Bunnett & B. Massingham, New Geography, P. 299]
(b) Road traffic noise
      Hong Kong is one of the busiest cities in the world. The traffic in Hong Kong is also
   very busy. Its vehicle density is almost the highest in the world. Tall buildings, narrow
   streets, buildings close to roads and highways are symbols of Hong Kong. Owing to
   these, the road traffic contributes a significant portion in noise pollution. It is estimated
   that the noise generated by traffic is louder than 70dB.
(c) Construction and industrial noise
      Construction area is a major source of noise pollution. The noise level of road
   drilling and piling operations can reach 110dB which is harmful to human. Workers in
   the construction area use lots of engines or tools which generate much noise. Industrial
   noise is usually confined in indoor environment. Workers in these areas who work for
   eight hours a day or more are surrounded by noise levels well over 100 dB.
(d) Neighborhood noise
      People will deliberately produce noise but at the same time, they complain others of
   producing noise. Neighborhood noise is noise from residential buildings and public
   places and is the type of noise pollution which receives most complaints in Hong Kong.
   Examples of neighborhood noise pollution include noise from playing mahjong,
   karaoke, loud music and conversation, doors slamming and baby screaming.



                              Noise complaints in Hong Kong 1995
               [Source: R. B. Bunnett & B. Massingham, New Geography, P. 299]
3. Effects
    Noise annoys and hurts people in both physiological and psychological ways. Problems
   related to noise include hearing loss, stress, high blood pressure, sleep loss, distraction,
   reduce in productivity of workers and a general reduction in the quality of life and
   opportunities for tranquility.
4. Noise control in Hong Kong
   (a) Noise Control Ordinance
         The Noise Control Ordinance was introduced in 1989 to help reduce the noise
       pollution. Its regulations cover noise generated from domestic premises and public
       places, construction activities such as piling, industrial or commercial premises,
       intruder alarm system installed in any premises or vehicle, individual items of plant or
       equipment such as hand-held breaker and air compressor, and motor vehicles. One
       example is to control traffic volume, vehicle mix and traffic conditions on roads. The
       ordinance specifies noise standards for the sources and has been progressively
       tightened to improve situation.



                           [Source: Environment Hong Kong 2001, P. 72]
(b) Planning ahead
     Noise pollution has been exacerbated by limited space and poor planning in Hong
    Kong. The old Kai Tak Airport and the West Kowloon Corridor are good examples.
    The best solution is to have a good planning beforehand. Now, new towns are
    designed with early input from the EPD. For example, in Tung Chung, roads are not
    constructed right beside residents. They are separated by barriers and wide spaces.



                                  West Kowloon Corridor
                       [Source: Environment Hong Kong 2001, P. 61]
(c) Environmentally friendly noise measures
     Due to the bad planning in the past, some existing roads have been already
    constructed close to people and create great disturbances to the nearby residents at
    night. Some environmentally friendly solutions can be applied to reduce traffic noise.
    These measures include the traffic management and pedestrian schemes. The traffic
    management scheme has been implemented in 3 areas to forbid certain types of
    vehicles from using some streets at night. Regarding the pedestrian scheme, vehicles
    are not allowed to use some streets at a specified time. This scheme has been
    implemented at Mong Kong and Causeway Bay. These measures can effectively
    reduce noise pollution.



                                 Traffic Management Scheme
                        [Source: Environment Hong Kong 2001, P. 70]




                        [Source: Environment Hong Kong 2001, P. 71]
(d) Other controls
        The level or effect of noise can be minimized by several other ways. First,
    workers in noisy working environment can be protected by wearing earplugs or other
    ear protectors. Besides, noise can be absorbed and reduced by some materials. For
    example, rubber or plastic compression seals, which are set around the door edges,
    provide the best result of insulation when closing the door. Complete or partial
    enslosure of the sources of noise is always employed in constructing roads. Barriers
    can be used to change the path of noise and to produce a ‘shadow’ behind the barriers.
    For example, placing a wall between the road and building.




                     Table 3 : Sound Insulation Materials for Enclosures
      Material          Thickness      Surface         Sound Transmission Loss
                                       Density
                           (mm)                                   (dB)
                                       (kg/m2)      125Hz         500Hz    2,000Hz
  Plastered Brick           125          240          36            40       54
  Wall
  Compressed                56           25           22            27       35
  Strawboard
  Acoustic Panel            50           27           19            31       44
  (Sandwich type
  steel sheet with
  fibre glass)
  Chipboard                 19           11           17            25       26
  Plaster Board              9            7           15            24       32
  Plywood                    6           3.5           9            16       27

				
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posted:12/20/2011
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