The Effect of Sound and Noise on the Environment
Sound
- Derived from pressure waves in the air by the vibrations of solid
objects
- Example: plucking a guitar string
- Sound waves are compressional, longitudinal waves made by
variations in pressure moving in the same direction.
- Has frequency and wavelength
- Velocity of sound in air is 331m/s
- Different materials can transmit or absorb sound of different
frequencies.
Noise
- Incoherent sound that is perceived to be annoying due to:
- Noise falls into several categories that extrapolate their effect
on
hearing.
- Noise nuisances are subjective, some people are more sensitive or
find
particular things worse than others.
Human Interpretation of Sound:
- When sound waves reach the ear, the structures
within vibrate.
- Sudden forceful vibrations can rupture the
eardrum.
The Effect of Sound on Hearing:
- If the intensity of any sound is great, then
human ears may be injured due to damage to the anatomical structures of
the ear.
- Hearing loss usually, however, usually occurs
slowly over a long period of time.
Measuring Sound:
- Loudness is measured in decibels (dB).
- Loudness of a sound is dependent upon proximity
to source of sound.
- No damage will be done to the ear if the sound
level is below 80 dB
- Steady exposure to sounds higher than 80 dB can
have negative long term effects on hearing.
Noise levels of
common sounds
Pain
|
130 dB
|
|
120 dB |
Aircraft taking off
|
110 dB |
Loud Rock Music
|
100 dB |
Semi Truck (short term hazard)
|
90 dB |
Jack Hammer
|
80 dB |
Traffic (ocupational limit)
|
70 dB |
Conversation
|
60 dB |
Background office noise
|
50 dB |
Windmill
|
40 dB |
|
30 dB |
Quiet bedroom
|
20 dB |
|
10 dB |
Threshold of hearing
|
0 dB |
Sources
of Noise
- Sounds, or noises, that are loud, annoying, or
harmful to the human ear.
- Varies from sounds from airplanes, traffic,
motorized equipment, to loud music.
Negative Effects of Noise Pollution:
- Moderate to severe effects of noise pollution
- Sleep interference
- Speech interference
- Hazard to hearing from long-term exposure
- Hazard to hearing from short-term exposure
- Acoustic trauma – causes pain
Causes of Hearing Loss:
- Hearing loss is a lifelong process, but many
factors can expedite this process.
- Outside causes that influence hearing loss:
- Drum punctures
- Ringing results from fever, tumors, and
circulation changes.
- Infection of middle ear
- Bone overgrowth
- Loudness
Types of Hearing Loss Associated with Noise
Pollution:
- In all situations there is background noise,
sometimes however this background noise can interfere with normal
hearing.
- Noise trauma – sudden and long exposure to
sounds with high frequencies.
- A train passing by at high speeds is an
example of a source of noise trauma.
- Blast trauma – injury that occurs from a single
source that has an explosive shock wave.
- Exposure to TNT dynamite detonation
Frequency of Hearing Loss due to Noise Exposure
- Noise-induced hearing loss is a cumulative
process
- It also occurs randomly across the population
- Some people are more susceptible to hearing
loss than others
- Hearing generally decreases with age
- Some hearing loss is due to congenital
attributes.
- Often difficult to distinguish hearing loss that
is due to environmental effects and loss from other causes.
- Risk of noise exposure is calculated by:
- A measure of daily noise exposure
- Duration of exposure (months, years)
- Age of person
The
Figure below shows the percent of exposed population with hearing
loss greater than 25 dB for various noise levels and years of
exposure as given by the ISO 1999-1990 method. Hearing loss is
defined as average threshold shift at 500, 1000, 2000 and 3000 Hz.
Protection from Noise Pollution:
- Earmuffs
- Redirection of noise sources
- Curfew times
Reduction of Noise Pollution:
- Sound proofing materials absorb noise over a
wide range of frequencies.
- Layering wall panels
- Increasing wall insulation
- Separate living spaces from common spaces
- Sound barriers along highways
- Quieter motorized vehicles
- Use of destructive interference to cancel out
sounds
Learning to protect yourself from Noise Pollution:
- Always wear hearing protection when working
around loud noises
- Take breaks when working in noisy areas
- Limit exposure to loud music
- Have regular hearing tests for any loss of
hearing
References
