Characteristics of Noise Pollution


Noise is defined as unwanted sound. This implies that all noise is sound, and all noise is subjective. Some sort of noise is inevitable since there cannot be a noise-free environment. According to Akhionbare (2009), the characteristics of noise pollution are as follow:

1.      Wide Range Intensity: The sound intensity to which the human ear is exposed ranges from 1 billionth (0.000000001) watt to 10 millions watts. However, sound measurement is usually done in decibels (db) rather than the watt since the later can be clumsy to work with. In the decibel system, logarithms of the ratios of loudness are used to compare sound intensities.
2.      Noise is Basically a City Problem: This is to say that rural areas are relatively quite compared to the city. This can be explained by the fact of the close relationship between population density and ambient noise. In general, the higher the population density, the louder the city.
3.      Noise has Continued to Increase Over Time: Sound experts have estimated that ambient city noise in many areas of the USA has doubled in 20 years. Another investigation estimates that ambient city noise in Canada increases a half-decibel a year. It can be inferred from these findings that increase in the level of soundscape over time has to do with technological progress. (Akhionbare 2009).
4.      Frequency of Sound or Noise: Sound is the quickly varying pressure wave travelling through a medium. The number of pressure variation per sound is called the frequency of sound and it’s measured in Hertz (Hz) which is defined as cycles per second. The higher the frequency, the more high pitched a sound is perceived. The sound produced by drums has much lower frequencies than those produced by a whistle.
5.      Loudness and the Decibel Scale: another property of noise is it’s loudness. A loud noise usually has a larger pressure variation and a weak one has smaller pressure variation.

Table 1.1: Range of Noise Pollution and their Measurement
Source of noise
Decibels
Characteristics
Threshold of hearing
0
Audible
Normal breathing
10
Audible
Leaves rustling in the breeze
20
Very quiet
Hospital ward
20-80

Whispering
30
Very quite
Classroom
30-40
Quiet
Library
35
Quiet
Quite restaurant
50
Quite
Conversation/normal speech
60

Window air conditioner
60

Commercial office
60-65

Car passing(15 meters away)
70

Piano
80-85

Garbage disposal unit
80

Industrial workshop
85

Hearing loss after prolonged
85

Exposure


Vacuum cleaner
85

Heavy city traffic
90

Heavy truck(15 meter away)
90

Food blender
93

Gasoline lawn mower
96

Farm tractor
98

Subway train
100

Chain saw (sawmill)
110

Unmuffled motorcycle
110

Jet airplane (160 meters overhead)
120
Painful
Machine gun at close range
120
Painful
Jet air craft at take-off (Nunez 2013)                                                          145

145
Painful
(Source: Akhionbare, 2009).

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