Background Research
Noise Pollution
Noise
pollution is a big problem in the world today. The majority is caused by
mankind and is having massive effect to both us and other living things on this
planet we all call home.
Noise
pollution on land and sea can cause a number of problems for both the human
race and wildlife as a whole but in different ways, as the effects on the
humans is behavioral and physiological meaning it will cause a person to become
angry and aggressive towards other people. Persistent noise pollution can cause
more serious health problems with hearing such as tinnitus and complete hearing
loss. Other health problems linked noise pollution includes things like loss of
sleep, depression and panic attacks (Nicks J 2012).
A case study done in 2007 demonstrated that a
large number of premature deaths are being linked to noise pollution from car
alarms and other peoples Mp3 players. This is because music now a days is full
of low pulsating bass, which needs to be turned up loud for the effect it gives
making people less aware of what is going on around them causing accidental
deaths on the roads. In this study it
states that chronic and excessive traffic noise has implicated in the deaths of
3 per cent of people in Europe. This study also says that noise pollution
increases stress, which can lead to heart attacks (Coghlan 2007)
These are
only the effect to humans but when looking at the effects noise pollution has
when it comes to wildlife animals can be more devastating as it can cause a
death in certain animal species; this is because noise pollution in wildlife
area will rapidly reduce the living habitats. This means that the wildlife in
these areas have to move on making a natural imbalance in the food chain, but
more importantly noise pollution in the sea such as sonar sound being used by the
military services all around the world is cause major confusing to underwater
mammals communication and in turn forcing whales behavior to changes like more
vocalised whales such as the sperm whale to be silent and humpback whales to
lengthen their songs during the use of sonar sound, It also tends to make
whales beach themselves putting their lives in danger just to get away from
this low frequency noise pollution under water (Zirbel, 2011)
This recent
study ‘Tracking noise pollution at sea’ has outlined that noise pollution off the coast of
California has increased by double every decade since the 1960s. This study
also outlines the use of manmade low frequency noise in the range of 20 to 2000
hertz being used under water is putting the wildlife at risk, but the noise
pollution is having more effects on the whales as they communicate to one
another over large distances in low frequencies.
As stated above sonar sound is one of the main reasons
for noise pollution in the ocean but it is also essential for us humans to use
if we want to navigate the depths of the ocean as this statement gives an explanation of how
sonar works and an insight into how it is used in the military.
“How does sonar work?
Sonar (Sound Navigation and
Ranging) gives our submarines virtual "eyes" underwater. Sonar is
used primarily to detect ships and submarines. There are two types of sonar:
active and passive. When using active sonar, a submarine transmits a pulse of
sound into the water and listens for how long it takes to bounce off another
object such as a ship or submarine and return. This gives information about
that ship or submarine's direction and distance away. Unfortunately, if a
submarine uses active sonar, all the other sonar-capable ships and submarines
in the area would know that the submarine is there. Since the primary advantage
that submarines enjoy is stealth (other ships don't know where they are), most
submarines rarely use active sonar. Passive sonar listens for the sounds coming
from other ships and submarines. When a submarine uses passive sonar, it is
able to obtain information about other ships and submarines without revealing
its own position. Like detectives examining a crime scene, skilled sonar
operators can determine such things as ship speed, number of propellers and
even the exact kind of ship just by listening to the sounds.” (U.S Military 2011) So
we have to ask ourselves is sonar sound really worth keeping at the cost of
losing some of the worlds the marine life. Although is extremely useful to the
military services of the world it is still causing damaging effects to marine
wildlife?
As well as
the problems man-made low frequencies are causing for the whales communication
the over use of these low frequency sounds are also stopping the whales tracking
down their natural prey and it was found in the same study mentioning that
noise pollution in the sea is forcing a group of right whales to use more
energy to communicate with one and other, meaning the whale have to use louder
calls leaving them with less energy to hunt. (Gupta 2011)
Although it
looks bad at the minute for the marine life but we humans are trying to right
our wrongs as the same recent study ‘Tracking noise pollution at sea’ talks about new noise forecasting technique to help
track all the effects that human activity is having on sea life, it also states
that the information gained in this experiment will help reroute ships away
from vulnerable underwater wildlife.
Sound speed in water/air
After
establishing what the main causes and effect of noise pollution are it is just
as important to understand how that sound is travelling through the different
mediums i.e. liquid, air and solid.
So it is a well
documented fact that sound speed is not set at a constant and it depends on the
medium it is travelling through as the speed of sound is affected by a number
of factors when traveling through air such as the temperature and air
pressure. So bearing that in mind when
the temperature in the air raises the speed of sound increases. It is also known that sound travels faster in
other mediums such as steel, iron and water than in air as if a sound was
traveling a mile in 5 seconds in air it does that the same distance in 1 second
in water and a third of that in steel. (Bobick, J 1996)
Although sound travels faster through water there are
also environmental factors that can slow down the speed of sound as is affected
by the water pressure, which is known as hydrostatic pressure this is measured
in bars and as the sound travels deeper through the open ocean it gets slower
as the water pressure levels gets higher after every 33ft. (Farrington 2010
p.20)
As the water pressure is slowing the speed of the
sound down so is the temperature of the water at that depth the reasoning being
as like the pressure the deeper the sound travels the colder the temperature
gets. And it is a known that sound
travels through environments better if the temperature is higher. (Farrington
2010 p.21) The above information is important to this project because a section
of the soundscape has to sound like it is underwater and knowing how the sound
may travel in that type of environment well help in recreate it.
Hearing Ranges and Sound pick up
Knowing the
different speeds that sound travels at in different mediums links up nicely to
the functionality and pick up ranges of both groups involved is important
because sound travels faster in water the soundscape will need to change to
indicate both an underwater and on land environment. Meaning the sound that the
listener hears in the soundscape has been manipulated to sound, as if it is
underwater and from different perspectives.
Human Being
Average range of
hearing for any person is ranged approximately between 20 hertz through to
approximately 20 kilohertz. This varies for each individual as not everyone can
hear the lowest point of this hearing scale; this can be the same for the
highest points of the scale as well.
(figure 3)
The human ear is a great tool as we as humans use the
ear to determine what a sound is. The amazing thing about the human ear is that
it split into three different sections; the outer ear (pinna), which picks up
the sound and sends it towards the middle ear (ear canal, where the sound
travels along the ear canal making all the tiny hairs inside vibrate which
makes the tiny bones move that finally turns the sound into the inner ear
(cochlea) where this information is sent to the brain to be processed.
(Gunther, 2012)
Killer whale
The killer
whale’s hearing range is similar to that of a human beings in the sense that it
starts at 20Hz and tailors of around 17KHz which is amazing considering their
massive size as they can grow up to 33feet in size. Killer whales like dolphins
use low frequency clicks, whistles and scream-like pulses to communicate between
one and other as well as navigational propose.
As shown on this picture on the left killer
whales have ears on the outside of their head like humans but that is not how
they pick up sound. Where as a toothed whale such as the killer (figure 4) whale as it is more
communally known pick up sounds through their whole head as well as their ear
canal but the sound is transferred to the brain by a fat filled cavity in their
lower jaw-bone which vibrates the bones in the ear at the end of the jaw-bone.
(Bonner, 1989)
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